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Rajan-Babu IS, Dolzhenko E, Eberle MA, Friedman JM. Sequence composition changes in short tandem repeats: heterogeneity, detection, mechanisms and clinical implications. Nat Rev Genet 2024; 25:476-499. [PMID: 38467784 DOI: 10.1038/s41576-024-00696-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/19/2024] [Indexed: 03/13/2024]
Abstract
Short tandem repeats (STRs) are a class of repetitive elements, composed of tandem arrays of 1-6 base pair sequence motifs, that comprise a substantial fraction of the human genome. STR expansions can cause a wide range of neurological and neuromuscular conditions, known as repeat expansion disorders, whose age of onset, severity, penetrance and/or clinical phenotype are influenced by the length of the repeats and their sequence composition. The presence of non-canonical motifs, depending on the type, frequency and position within the repeat tract, can alter clinical outcomes by modifying somatic and intergenerational repeat stability, gene expression and mutant transcript-mediated and/or protein-mediated toxicities. Here, we review the diverse structural conformations of repeat expansions, technological advances for the characterization of changes in sequence composition, their clinical correlations and the impact on disease mechanisms.
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Affiliation(s)
- Indhu-Shree Rajan-Babu
- Department of Medical Genetics, The University of British Columbia, and Children's & Women's Hospital, Vancouver, British Columbia, Canada.
| | | | | | - Jan M Friedman
- Department of Medical Genetics, The University of British Columbia, and Children's & Women's Hospital, Vancouver, British Columbia, Canada
- BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada
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2
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Persico T, Tranquillo ML, Seracchioli R, Zuccarello D, Sorrentino U. PGT-M for Premature Ovarian Failure Related to CGG Repeat Expansion of the FMR1 Gene. Genes (Basel) 2023; 15:6. [PMID: 38275588 PMCID: PMC10815814 DOI: 10.3390/genes15010006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Revised: 12/14/2023] [Accepted: 12/15/2023] [Indexed: 01/27/2024] Open
Abstract
Primary ovarian failure (POF) is caused by follicle exhaustion and is associated with menstrual irregularities and elevated gonadotropin levels, which lead to infertility before the age of 40 years. The etiology of POI is mostly unknown, but a heterogeneous genetic and familial background can be identified in a subset of cases. Abnormalities in the fragile X mental retardation 1 gene (FMR1) are among the most prevalent monogenic causes of POI. These abnormalities are caused by the expansion of an unstable CGG repeat in the 5' untranslated region of FMR1. Expansions over 200 repeats cause fragile X syndrome (FXS), whereas expansions between 55 and 200 CGG repeats, which are defined as a fragile X premutation, have been associated with premature ovarian failure type 1 (POF1) in heterozygous females. Preimplantation genetic testing for monogenic diseases (PGT-M) can be proposed when the female carries a premutation or a full mutation. In this narrative review, we aim to recapitulate the clinical and molecular features of POF1 and their implications in the context of PGT-M.
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Affiliation(s)
- Tiziana Persico
- Medically Assisted Procreation Center, Maternal and Child Department, Beauregard Hospital, Valle D’Aosta Local Public Health, 11100 Aoste, Italy
| | - Maria Lucrezia Tranquillo
- Department of Medical and Surgical Sciences, University of Bologna, 40126 Bologna, Italy; (M.L.T.); (R.S.)
| | - Renato Seracchioli
- Department of Medical and Surgical Sciences, University of Bologna, 40126 Bologna, Italy; (M.L.T.); (R.S.)
- Division of Gynaecology and Human Reproduction Physiopathology, IRCCS Azienda Ospedaliero, University of Bologna, 40138 Bologna, Italy
| | - Daniela Zuccarello
- Clinical Genetics and Epidemiology Unit, University of Padova, 35128 Padova, Italy; (D.Z.); (U.S.)
| | - Ugo Sorrentino
- Clinical Genetics and Epidemiology Unit, University of Padova, 35128 Padova, Italy; (D.Z.); (U.S.)
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Annear DJ, Kooy RF. Unravelling the link between neurodevelopmental disorders and short tandem CGG-repeat expansions. Emerg Top Life Sci 2023; 7:265-275. [PMID: 37768318 PMCID: PMC10754333 DOI: 10.1042/etls20230021] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 08/23/2023] [Accepted: 09/11/2023] [Indexed: 09/29/2023]
Abstract
Neurodevelopmental disorders (NDDs) encompass a diverse group of disorders characterised by impaired cognitive abilities and developmental challenges. Short tandem repeats (STRs), repetitive DNA sequences found throughout the human genome, have emerged as potential contributors to NDDs. Specifically, the CGG trinucleotide repeat has been implicated in a wide range of NDDs, including Fragile X Syndrome (FXS), the most common inherited form of intellectual disability and autism. This review focuses on CGG STR expansions associated with NDDs and their impact on gene expression through repeat expansion-mediated epigenetic silencing. We explore the molecular mechanisms underlying CGG-repeat expansion and the resulting epigenetic modifications, such as DNA hypermethylation and gene silencing. Additionally, we discuss the involvement of other CGG STRs in neurodevelopmental diseases. Several examples, including FMR1, AFF2, AFF3, XYLT1, FRA10AC1, CBL, and DIP2B, highlight the complex relationship between CGG STR expansions and NDDs. Furthermore, recent advancements in this field are highlighted, shedding light on potential future research directions. Understanding the role of STRs, particularly CGG-repeats, in NDDs has the potential to uncover novel diagnostic and therapeutic strategies for these challenging disorders.
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Affiliation(s)
- Dale J Annear
- Department of Medical Genetics, University of Antwerp, Antwerp, Belgium
| | - R Frank Kooy
- Department of Medical Genetics, University of Antwerp, Antwerp, Belgium
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Kargar M, Hagerman RJ, Martínez-Cerdeño V. Neurodegeneration of White and Gray Matter in the Hippocampus with FXTAS. Int J Mol Sci 2023; 24:17266. [PMID: 38139097 PMCID: PMC10743470 DOI: 10.3390/ijms242417266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 11/07/2023] [Accepted: 12/05/2023] [Indexed: 12/24/2023] Open
Abstract
Fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disorder that affects older premutation carriers (55-200 CGG repeats) of the fragile X gene. Despite the high prevalence of the FXTAS disorder, neuropathology studies of individuals affected by FXTAS are limited. We performed hematoxylin and eosin (H&E) staining in the hippocampus of 26 FXTAS cases and analyzed the tissue microscopically. The major neuropathological characteristics were white matter disease, intranuclear inclusions in neurons and astrocytes, and neuron loss. Astrocytes contained more and larger inclusions than neurons. There was a negative correlation between age of death and CGG repeat length in cases over the age of 60. The number of astroglial inclusions (CA3 and dentate gyrus) and the number of CA3 neuronal inclusions increased with elevated CGG repeat length. In the two cases with a CGG repeat size less than 65, FXTAS intranuclear inclusions were not present in the hippocampus, while in the two cases with less than 70 (65-70) CGG repeat expansion, neurons and astrocytes with inclusions were occasionally identified in the CA1 sub-region. These findings add hippocampus neuropathology to the previously reported changes in other areas of the brain in FXTAS patients, with implications for understanding FXTAS pathogenesis.
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Affiliation(s)
- Maryam Kargar
- Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children, Sacramento, CA 95817, USA
- Department of Pathology and Laboratory Medicine, UC Davis School of Medicine, Sacramento, CA 95817, USA
| | - Randi J. Hagerman
- MIND Institute, UC Davis School of Medicine, Sacramento, CA 95817, USA;
| | - Verónica Martínez-Cerdeño
- Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children, Sacramento, CA 95817, USA
- Department of Pathology and Laboratory Medicine, UC Davis School of Medicine, Sacramento, CA 95817, USA
- MIND Institute, UC Davis School of Medicine, Sacramento, CA 95817, USA;
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Hou F, Mao A, Shan S, Li Y, Meng W, Zhan J, Nie W, Jin H. Evaluating the clinical utility of a long-read sequencing-based approach in genetic testing of fragile-X syndrome. Clin Chim Acta 2023; 551:117614. [PMID: 38375623 DOI: 10.1016/j.cca.2023.117614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 10/19/2023] [Accepted: 10/22/2023] [Indexed: 02/21/2024]
Abstract
BACKGROUND Fragile X syndrome (FXS) arises from the FMR1 CGG expansion. Comprehensive genetic testing for FMR1 CGG expansions, AGG interruptions, and microdeletions is essential to provide genetic counseling for females carrying premutation alleles. However, conventional PCR-based FMR1 assays mainly focus on CGG repeats, and could detect AGG interruption only in males. METHODS The clinical utility of a long-read sequencing-based assay termed comprehensive analysis of FXS (CAFXS) was evaluated in 238 high-risk samples by comparing to conventional PCR assays. RESULTS PCR assays identified five premuation and three full mutation categories alleles in all the samples, and CAFXS successfully called all the FMR1 CGG expansion. CAFXS identified 24-bp microdeletions upstream to the trinucleotide region with 30 CGG repeats, which was miscalled by the length-based PCR methods. CAFXS also identified a 187-bp deletion in about 1/7 of the sequencing reads in a male patient with mosaic full mutation alleles. CAFXS allowed for precise constructing the FMR1 CGG repeat and AGG interruption pattern in all the samples, and identified a novel and alternative CGA interruption in one normal female sample. CONCLUSIONS CAFXS represents a more comprehensive and accurate approach for FXS genetic testing that potentially enables more informed genetic counseling compared to PCR-based methods.
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Affiliation(s)
- Fei Hou
- Department of Prenatal Diagnosis, Jinan Maternal and Child Health Hospital, Jinan 250001, Shandong Province, China
| | - Aiping Mao
- Berry Genomics Corporation, Beijing 102200, China
| | - Shan Shan
- Department of Prenatal Diagnosis, Jinan Maternal and Child Health Hospital, Jinan 250001, Shandong Province, China
| | - Yan Li
- Department of Prenatal Diagnosis, Jinan Maternal and Child Health Hospital, Jinan 250001, Shandong Province, China
| | - Wanli Meng
- Berry Genomics Corporation, Beijing 102200, China
| | - Jiahan Zhan
- Berry Genomics Corporation, Beijing 102200, China
| | - Wenying Nie
- Department of Prenatal Diagnosis, Jinan Maternal and Child Health Hospital, Jinan 250001, Shandong Province, China
| | - Hua Jin
- Department of Prenatal Diagnosis, Jinan Maternal and Child Health Hospital, Jinan 250001, Shandong Province, China.
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Protic D, Polli R, Hwang YH, Mendoza G, Hagerman R, Durbin-Johnson B, Hayward BE, Usdin K, Murgia A, Tassone F. Activation Ratio Correlates with IQ in Female Carriers of the FMR1 Premutation. Cells 2023; 12:1711. [PMID: 37443745 PMCID: PMC10341054 DOI: 10.3390/cells12131711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2023] [Revised: 06/17/2023] [Accepted: 06/21/2023] [Indexed: 07/15/2023] Open
Abstract
Carriers of the FMR1 premutation (PM) allele are at risk of one or more clinical conditions referred to as FX premutation-associated conditions (FXPAC). Since the FMR1 gene is on the X chromosome, the activation ratio (AR) may impact the risk, age of onset, progression, and severity of these conditions. The aim of this study was to evaluate the reliability of AR measured using different approaches and to investigate potential correlations with clinical outcomes. Molecular and clinical assessments were obtained for 30 PM female participants, and AR was assessed using both Southern blot analysis (AR-Sb) and methylation PCR (AR-mPCR). Higher ARs were associated with lower FMR1 transcript levels for any given repeat length. The higher AR-Sb was significantly associated with performance, verbal, and full-scale IQ scores, confirming previous reports. However, the AR-mPCR was not significantly associated (p > 0.05) with these measures. Similarly, the odds of depression and the number of medical conditions were correlated with higher AR-Sb but not correlated with a higher AR-mPCR. This study suggests that AR-Sb may be a more reliable measure of the AR in female carriers of PM alleles. However, further studies are warranted in a larger sample size to fully evaluate the methylation status in these participants and how it may affect the clinical phenotype.
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Affiliation(s)
- Dragana Protic
- Department of Pharmacology, Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia;
| | - Roberta Polli
- Laboratory of Molecular Genetics of Neurodevelopment, Department of Woman and Child Health, University of Padova, 35128 Padova, Italy; (R.P.); (A.M.)
- Fondazione Istituto di Ricerca Pediatrica, Città della Speranza, 35128 Padova, Italy
| | - Ye Hyun Hwang
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California Davis, Sacramento, CA 95817, USA; (Y.H.H.); (G.M.)
| | - Guadalupe Mendoza
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California Davis, Sacramento, CA 95817, USA; (Y.H.H.); (G.M.)
| | - Randi Hagerman
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute UCDH, University of California Davis, Sacramento, CA 95817, USA;
- Department of Pediatrics, School of Medicine, University of California Davis, Sacramento, CA 95817, USA
| | - Blythe Durbin-Johnson
- Department of Public Health Sciences, Division of Biostatistics, University of California, Davis, CA 95616, USA;
| | - Bruce E. Hayward
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA; (B.E.H.); (K.U.)
| | - Karen Usdin
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA; (B.E.H.); (K.U.)
| | - Alessandra Murgia
- Laboratory of Molecular Genetics of Neurodevelopment, Department of Woman and Child Health, University of Padova, 35128 Padova, Italy; (R.P.); (A.M.)
- Fondazione Istituto di Ricerca Pediatrica, Città della Speranza, 35128 Padova, Italy
| | - Flora Tassone
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California Davis, Sacramento, CA 95817, USA; (Y.H.H.); (G.M.)
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute UCDH, University of California Davis, Sacramento, CA 95817, USA;
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Taghavi A, Baisden JT, Childs-Disney JL, Yildirim I, Disney M. Conformational dynamics of RNA G4C2 and G2C4 repeat expansions causing ALS/FTD using NMR and molecular dynamics studies. Nucleic Acids Res 2023; 51:5325-5340. [PMID: 37216594 PMCID: PMC10287959 DOI: 10.1093/nar/gkad403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2023] [Revised: 04/15/2023] [Accepted: 05/03/2023] [Indexed: 05/24/2023] Open
Abstract
G4C2 and G2C4 repeat expansions in chromosome 9 open reading frame 72 (C9orf72) are the most common cause of genetically defined amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), or c9ALS/FTD. The gene is bidirectionally transcribed, producing G4C2 repeats [r(G4C2)exp] and G2C4 repeats [r(G2C4)exp]. The c9ALS/FTD repeat expansions are highly structured, and structural studies showed that r(G4C2)exp predominantly folds into a hairpin with a periodic array of 1 × 1 G/G internal loops and a G-quadruplex. A small molecule probe revealed that r(G4C2)exp also adopts a hairpin structure with 2 × 2 GG/GG internal loops. We studied the conformational dynamics adopted by 2 × 2 GG/GG loops using temperature replica exchange molecular dynamics (T-REMD) and further characterized the structure and underlying dynamics using traditional 2D NMR techniques. These studies showed that the loop's closing base pairs influence both structure and dynamics, particularly the configuration adopted around the glycosidic bond. Interestingly, r(G2C4) repeats, which fold into an array of 2 × 2 CC/CC internal loops, are not as dynamic. Collectively, these studies emphasize the unique sensitivity of r(G4C2)exp to small changes in stacking interactions, which is not observed in r(G2C4)exp, providing important considerations for further principles in structure-based drug design.
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Affiliation(s)
- Amirhossein Taghavi
- Department of Chemistry, Scripps Research and The Herbert Wertheim UF-Scripps Institute for Biomedical Research & Innovation, 130 Scripps Way, 3A1 Jupiter, FL 33458, USA
| | - Jared T Baisden
- Department of Chemistry, Scripps Research and The Herbert Wertheim UF-Scripps Institute for Biomedical Research & Innovation, 130 Scripps Way, 3A1 Jupiter, FL 33458, USA
| | - Jessica L Childs-Disney
- Department of Chemistry, Scripps Research and The Herbert Wertheim UF-Scripps Institute for Biomedical Research & Innovation, 130 Scripps Way, 3A1 Jupiter, FL 33458, USA
| | - Ilyas Yildirim
- Department of Chemistry and Biochemistry, Florida Atlantic University, 5353 Parkside Drive, Jupiter, FL 33458, USA
| | - Matthew D Disney
- Department of Chemistry, Scripps Research and The Herbert Wertheim UF-Scripps Institute for Biomedical Research & Innovation, 130 Scripps Way, 3A1 Jupiter, FL 33458, USA
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Gene-Environment Interactions in Repeat Expansion Diseases: Mechanisms of Environmentally Induced Repeat Instability. Biomedicines 2023; 11:biomedicines11020515. [PMID: 36831049 PMCID: PMC9953593 DOI: 10.3390/biomedicines11020515] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Revised: 02/06/2023] [Accepted: 02/07/2023] [Indexed: 02/12/2023] Open
Abstract
Short tandem repeats (STRs) are units of 1-6 base pairs that occur in tandem repetition to form a repeat tract. STRs exhibit repeat instability, which generates expansions or contractions of the repeat tract. Over 50 diseases, primarily affecting the central nervous system and muscles, are characterized by repeat instability. Longer repeat tracts are typically associated with earlier age of onset and increased disease severity. Environmental exposures are suspected to play a role in the pathogenesis of repeat expansion diseases. Here, we review the current knowledge of mechanisms of environmentally induced repeat instability in repeat expansion diseases. The current evidence demonstrates that environmental factors modulate repeat instability via DNA damage and induction of DNA repair pathways, with distinct mechanisms for repeat expansion and contraction. Of particular note, oxidative stress is a key mediator of environmentally induced repeat instability. The preliminary evidence suggests epigenetic modifications as potential mediators of environmentally induced repeat instability. Future research incorporating an array of environmental exposures, new human cohorts, and improved model systems, with a continued focus on cell-types, tissues, and critical windows, will aid in identifying mechanisms of environmentally induced repeat instability. Identifying environmental modulators of repeat instability and their mechanisms of action will inform preventions, therapies, and public health measures.
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Shahid R, Yasin M, Rehman ZU, Jadoon H, Tahir H, Meraj N, Khan N, Zubair M, Zulfiqar I, Nowshid M, Azeem A, Jabeen M, Hameed A, Saleha S. Maternal FMR1 alleles expansion in newborns during transmission: a prospective cohort study. Pediatr Res 2023; 93:720-724. [PMID: 35681093 DOI: 10.1038/s41390-022-02128-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Revised: 04/05/2022] [Accepted: 05/17/2022] [Indexed: 11/09/2022]
Abstract
INTRODUCTION The CGG repeats in the 5' untranslated region of the fragile X mental retardation 1 gene (FMR1) gene shows increased instability upon maternal transmission. Maternal FMR1 intermediate (45-54 repeats) and premutation (PM: 55-<200 repeats) alleles usually expand to full mutation (>200 repeats) alleles in offspring and consequently, cause fragile X syndrome (FXS) in them. METHODS In a prospective cohort study, Pakistani pregnant women in prenatal care were first screened for FMR1 expanded alleles. In the follow-up, pregnancy outcomes in women carrying FMR1 expanded alleles were recorded and their newborn offspring were also screened for FXS. RESULTS In a total of 1950 pregnant women, 89 (4.6%) were detected carriers for FMR1 expanded alleles; however, rates of detection of expanded alleles were found significantly high in women with a history of FXS. In addition, miscarriages and birth of affected newborns with FXS were significantly more common in women carrying large size PM alleles and had a history of FXS (P = 0.0494 and P = 0.0494, respectively). CONCLUSIONS The current study provides the first evidence of screening Pakistani pregnant women for FMR1 expanded alleles in prenatal care. Moreover, the miscarriage was also detected as a clinical predictor for FXS. IMPACT Offspring would have a higher risk of developing FXS due to maternal FMR1 alleles expansions during transmission. This is the first prospective cohort study in Pakistan for finding FMR1 allelic status of pregnant women and their newborn offspring in follow-up. The robust offspring risk for FXS estimated in this study may be valuable information for genetic counseling of women carriers for FMR1 expanded alleles. The family history and miscarriage were detected as effective indicators for FXS carrier screening in Pakistani women.
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Affiliation(s)
- Rabia Shahid
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology (KUST), Kohat, 26000, Khyber Pakhtunkhwa, Pakistan
| | - Muhammad Yasin
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology (KUST), Kohat, 26000, Khyber Pakhtunkhwa, Pakistan
| | - Zia Ur Rehman
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology (KUST), Kohat, 26000, Khyber Pakhtunkhwa, Pakistan
| | - Humaira Jadoon
- Department of Obstetrics & Gynecology, Ayub Medical Institute, Abbottabad, 22010, Khyber Pakhtunkhwa, Pakistan
| | - Haleema Tahir
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology (KUST), Kohat, 26000, Khyber Pakhtunkhwa, Pakistan
| | - Neelam Meraj
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology (KUST), Kohat, 26000, Khyber Pakhtunkhwa, Pakistan
| | - Niamat Khan
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology (KUST), Kohat, 26000, Khyber Pakhtunkhwa, Pakistan
| | - Maria Zubair
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology (KUST), Kohat, 26000, Khyber Pakhtunkhwa, Pakistan
| | - Irba Zulfiqar
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology (KUST), Kohat, 26000, Khyber Pakhtunkhwa, Pakistan
| | - Maha Nowshid
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology (KUST), Kohat, 26000, Khyber Pakhtunkhwa, Pakistan
| | - Arfa Azeem
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology (KUST), Kohat, 26000, Khyber Pakhtunkhwa, Pakistan
| | - Musarrat Jabeen
- Department of Obstetrics and Gynecology, Liaqat Memorial Hospital, KIMS, Kohat, 26000, Khyber Pakhtunkhwa, Pakistan
| | - Abdul Hameed
- Institute of Biomedical and Genetic Engineering (IBGE), Islamabad, 44000, Pakistan
| | - Shamim Saleha
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology (KUST), Kohat, 26000, Khyber Pakhtunkhwa, Pakistan.
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Abstract
The fragile X-related disorders are an important group of hereditary disorders that are caused by expanded CGG repeats in the 5' untranslated region of the FMR1 gene or by mutations in the coding sequence of this gene. Two categories of pathological CGG repeats are associated with these disorders, full mutation alleles and shorter premutation alleles. Individuals with full mutation alleles develop fragile X syndrome, which causes autism and intellectual disability, whereas those with premutation alleles, which have shorter CGG expansions, can develop fragile X-associated tremor/ataxia syndrome, a progressive neurodegenerative disease. Thus, fragile X-related disorders can manifest as neurodegenerative or neurodevelopmental disorders, depending on the size of the repeat expansion. Here, we review mouse models of fragile X-related disorders and discuss how they have informed our understanding of neurodegenerative and neurodevelopmental disorders. We also assess the translational value of these models for developing rational targeted therapies for intellectual disability and autism disorders.
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Affiliation(s)
- Rob Willemsen
- Department of Clinical Genetics, Erasmus University Medical Center, 3015 CN Rotterdam, the Netherlands. Department of Medical Genetics, University of Antwerp, 2000 Antwerp, Belgium
| | - R Frank Kooy
- Department of Clinical Genetics, Erasmus University Medical Center, 3015 CN Rotterdam, the Netherlands. Department of Medical Genetics, University of Antwerp, 2000 Antwerp, Belgium
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Ryan NM, Heron EA. Evidence for parent-of-origin effects in autism spectrum disorder: a narrative review. J Appl Genet 2023; 64:303-317. [PMID: 36710277 PMCID: PMC10076404 DOI: 10.1007/s13353-022-00742-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 12/08/2022] [Accepted: 12/15/2022] [Indexed: 01/31/2023]
Abstract
Autism spectrum disorder (ASD) is a heterogeneous group of early-onset neurodevelopmental disorders known to be highly heritable with a complex genetic architecture. Abnormal brain developmental trajectories that impact synaptic functioning, excitation-inhibition balance and brain connectivity are now understood to play a central role in ASD. Ongoing efforts to identify the genetic underpinnings still prove challenging, in part due to phenotypic and genetic heterogeneity.This review focuses on parent-of-origin effects (POEs), where the phenotypic effect of an allele depends on its parental origin. POEs include genomic imprinting, transgenerational effects, mitochondrial DNA, sex chromosomes and mutational transmission bias. The motivation for investigating these mechanisms in ASD has been driven by their known impacts on early brain development and brain functioning, in particular for the most well-documented POE, genomic imprinting. Moreover, imprinting is implicated in syndromes such as Angelman and Prader-Willi, which frequently share comorbid symptoms with ASD. In addition to other regions in the genome, this comprehensive review highlights the 15q11-q13 and 7q chromosomal regions as well as the mitochondrial DNA as harbouring the majority of currently identified POEs in ASD.
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Affiliation(s)
- Niamh M Ryan
- Neuropsychiatric Genetics Research Group, Department of Psychiatry, Trinity College Dublin, Dublin, Ireland
| | - Elizabeth A Heron
- Neuropsychiatric Genetics Research Group, Department of Psychiatry, Trinity College Dublin, Dublin, Ireland.
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Ovarian Reserve Disorders, Can We Prevent Them? A Review. Int J Mol Sci 2022; 23:ijms232315426. [PMID: 36499748 PMCID: PMC9737352 DOI: 10.3390/ijms232315426] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 11/28/2022] [Accepted: 11/29/2022] [Indexed: 12/12/2022] Open
Abstract
The ovarian reserve is finite and begins declining from its peak at mid-gestation until only residual follicles remain as women approach menopause. Reduced ovarian reserve, or its extreme form, premature ovarian insufficiency, stems from multiple factors, including developmental, genetic, environmental exposures, autoimmune disease, or medical/surgical treatment. In many cases, the cause remains unknown and resulting infertility is not ultimately addressed by assisted reproductive technologies. Deciphering the mechanisms that underlie disorders of ovarian reserve could improve the outcomes for patients struggling with infertility, but these disorders are diverse and can be categorized in multiple ways. In this review, we will explore the topic from a perspective that emphasizes the prevention or mitigation of ovarian damage. The most desirable mode of fertoprotection is primary prevention (intervening before ablative influence occurs), as identifying toxic influences and deciphering the mechanisms by which they exert their effect can reduce or eliminate exposure and damage. Secondary prevention in the form of screening is not recommended broadly. Nevertheless, in some instances where a known genetic background exists in discrete families, screening is advised. As part of prenatal care, screening panels include some genetic diseases that can lead to infertility or subfertility. In these patients, early diagnosis could enable fertility preservation or changes in family-building plans. Finally, Tertiary Prevention (managing disease post-diagnosis) is critical. Reduced ovarian reserve has a major influence on physiology beyond fertility, including delayed/absent puberty or premature menopause. In these instances, proper diagnosis and medical therapy can reduce adverse effects. Here, we elaborate on these modes of prevention as well as proposed mechanisms that underlie ovarian reserve disorders.
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Rosario R, Stewart HL, Choudhury NR, Michlewski G, Charlet‐Berguerand N, Anderson RA. Evidence for a fragile X messenger ribonucleoprotein 1 (FMR1) mRNA gain-of-function toxicity mechanism contributing to the pathogenesis of fragile X-associated premature ovarian insufficiency. FASEB J 2022; 36:e22612. [PMID: 36250920 PMCID: PMC9828574 DOI: 10.1096/fj.202200468rr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Revised: 09/22/2022] [Accepted: 10/03/2022] [Indexed: 01/12/2023]
Abstract
Fragile X-associated premature ovarian insufficiency (FXPOI) is among a family of disorders caused by expansion of a CGG trinucleotide repeat sequence located in the 5' untranslated region (UTR) of the fragile X messenger ribonucleoprotein 1 (FMR1) gene on the X chromosome. Women with FXPOI have a depleted ovarian follicle population, resulting in amenorrhea, hypoestrogenism, and loss of fertility before the age of 40. FXPOI is caused by expansions of the CGG sequence to lengths between 55 and 200 repeats, known as a FMRI premutation, however the mechanism by which the premutation drives disease pathogenesis remains unclear. Two main hypotheses exist, which describe an mRNA toxic gain-of-function mechanism or a protein-based mechanism, where repeat-associated non-AUG (RAN) translation results in the production of an abnormal protein, called FMRpolyG. Here, we have developed an in vitro granulosa cell model of the FMR1 premutation by ectopically expressing CGG-repeat RNA and FMRpolyG protein. We show that expanded CGG-repeat RNA accumulated in intranuclear RNA structures, and these aggregates were able to cause significant granulosa cell death independent of FMRpolyG expression. Using an innovative RNA pulldown, mass spectrometry-based approach we have identified proteins that are specifically sequestered by CGG RNA aggregates in granulosa cells in vitro, and thus may be deregulated as consequence of this interaction. Furthermore, we have demonstrated reduced expression of three proteins identified via our RNA pulldown (FUS, PA2G4 and TRA2β) in ovarian follicles in a FMR1 premutation mouse model. Collectively, these data provide evidence for the contribution of an mRNA gain-of-function mechanism to FXPOI disease biology.
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Affiliation(s)
- Roseanne Rosario
- MRC Centre for Reproductive Health, Queen's Medical Research InstituteUniversity of EdinburghEdinburghUK,Biomedical SciencesUniversity of EdinburghEdinburghUK
| | - Hazel L. Stewart
- MRC Centre for Reproductive Health, Queen's Medical Research InstituteUniversity of EdinburghEdinburghUK
| | | | - Gracjan Michlewski
- Infection MedicineUniversity of EdinburghEdinburghUK,Zhejiang University‐University of Edinburgh InstituteZhejiang UniversityZhejiangP.R. China,Dioscuri Centre for RNA‐Protein Interactions in Human Health and DiseaseInternational Institute of Molecular and Cell Biology in WarsawWarsawPoland
| | - Nicholas Charlet‐Berguerand
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC)INSERM U 1258, CNRS UMR 7104, Université of StrasbourgIllkirchFrance
| | - Richard A. Anderson
- MRC Centre for Reproductive Health, Queen's Medical Research InstituteUniversity of EdinburghEdinburghUK
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Liang Q, Liu Y, Liu Y, Duan R, Meng W, Zhan J, Xia J, Mao A, Liang D, Wu L. Comprehensive Analysis of Fragile X Syndrome: Full Characterization of the FMR1 Locus by Long-Read Sequencing. Clin Chem 2022; 68:1529-1540. [PMID: 36171182 DOI: 10.1093/clinchem/hvac154] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 07/21/2022] [Indexed: 11/14/2022]
Abstract
BACKGROUND Fragile X syndrome (FXS) is the most frequent cause of inherited X-linked intellectual disability. Conventional FXS genetic testing methods mainly focus on FMR1 CGG expansions and fail to identify AGG interruptions, rare intragenic variants, and large gene deletions. METHODS A long-range PCR and long-read sequencing-based assay termed comprehensive analysis of FXS (CAFXS) was developed and evaluated in Coriell and clinical samples by comparing to Southern blot analysis and triplet repeat-primed PCR (TP-PCR). RESULTS CAFXS accurately detected the number of CGG repeats in the range of 93 to at least 940 with mass fraction of 0.5% to 1% in the background of normal alleles, which was 2-4-fold analytically more sensitive than TP-PCR. All categories of mutations detected by control methods, including full mutations in 30 samples, were identified by CAFXS for all 62 clinical samples. CAFXS accurately determined AGG interruptions in all 133 alleles identified, even in mosaic alleles. CAFXS successfully identified 2 rare intragenic variants including the c.879A > C variant in exon 9 and a 697-bp microdeletion flanking upstream of CGG repeats, which disrupted primer annealing in TP-PCR assay. In addition, CAFXS directly determined the breakpoints of a 237.1-kb deletion and a 774.0-kb deletion encompassing the entire FMR1 gene in 2 samples. CONCLUSIONS Long-read sequencing-based CAFXS represents a comprehensive assay for identifying FMR1 CGG expansions, AGG interruptions, rare intragenic variants, and large gene deletions, which greatly improves the genetic screening and diagnosis for FXS.
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Affiliation(s)
- Qiaowei Liang
- Department of Medical Genetics, Hunan Jiahui Genetics Hospital, Changsha, Hunan, China
| | - Yingdi Liu
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Yaning Liu
- Department of Medical Genetics, Hunan Jiahui Genetics Hospital, Changsha, Hunan, China
| | - Ranhui Duan
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Wanli Meng
- Berry Genomics Corporation, Beijing, China
| | | | - Jiahui Xia
- Department of Medical Genetics, Hunan Jiahui Genetics Hospital, Changsha, Hunan, China
| | - Aiping Mao
- Berry Genomics Corporation, Beijing, China
| | - Desheng Liang
- Department of Medical Genetics, Hunan Jiahui Genetics Hospital, Changsha, Hunan, China.,Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Lingqian Wu
- Department of Medical Genetics, Hunan Jiahui Genetics Hospital, Changsha, Hunan, China.,Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
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15
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Shulman Y, Kalma Y, Malcov M, Kopel R, Fouks Y, Azem F, Almog B, Cohen Y. The impact of fragile X premutation carrier status on embryo morphokinetic development. Reprod Biomed Online 2022; 45:884-889. [DOI: 10.1016/j.rbmo.2022.06.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2022] [Revised: 05/25/2022] [Accepted: 06/20/2022] [Indexed: 10/17/2022]
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16
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Rajan-Babu IS, Lian M, Chong SS. Triplet-Primed PCR Assays for Accurate Screening of FMR1 CGG Repeat Expansion and Genotype Verification. Curr Protoc 2022; 2:e427. [PMID: 35609145 DOI: 10.1002/cpz1.427] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Fragile X syndrome and other fragile X-associated disorders are caused by the full-mutation (>200 copies) and premutation (55 to 200 copies) expansion, respectively, of the CGG short tandem repeat in the fragile X messenger ribonucleoprotein 1 (FMR1) gene. Clinical diagnostic laboratories use Southern blot analysis and polymerase chain reaction (PCR)-based tests to detect and/or size the FMR1 CGG repeats. The development of sensitive and high-throughput triplet-primed PCR (TP-PCR) assays has diminished the need to subject all samples to Southern blot analysis, which is both labor- and time-intensive. In this article, we describe two direct TP-PCR (dTP-PCR) assays for the detection of FMR1 CGG repeat expansions. We outline a protocol that is based on melting curve analysis of dTP-PCR amplicons for a rapid and cost-effective first-tier screening and identification of individuals with premutation and full-mutation expansions. We also describe a protocol that employs capillary electrophoresis to resolve the dTP-PCR amplicon fragments and to estimate the repeat sizes of normal (5 to 44 copies), intermediate (45 to 54 copies), and premutation alleles, as well as to detect full mutations and determine the structure of the FMR1 alleles. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Direct triplet-primed PCR master mix preparation and amplification of the FMR1 CGG repeat locus for melting curve analysis Basic Protocol 2: Melting curve analysis of direct triplet-primed PCR amplicons on the Rotor-Gene Q MD × 5plex high-resolution melt platform Alternate Protocol: Melting curve analysis of direct triplet-primed PCR amplicons on the LightCycler 480 system Basic Protocol 3: Generation of direct triplet-primed PCR melting curve analysis profiles Basic Protocol 4: Direct triplet-primed PCR master mix preparation and amplification of the FMR1 CGG repeat locus for capillary electrophoresis Basic Protocol 5: Generation of control FMR1 plasmids for direct triplet-primed PCR melting curve analysis Basic Protocol 6: Sanger sequencing assay to verify FMR1 CGG repeat size and structure of plasmid DNA controls.
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Affiliation(s)
- Indhu-Shree Rajan-Babu
- Department of Pediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.,Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.,Children's & Women's Hospital, Vancouver, British Columbia, Canada
| | - Mulias Lian
- Khoo Teck Puat-National University Children's Medical Institute, National University Hospital, Singapore, Singapore
| | - Samuel S Chong
- Department of Pediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.,Department of Obstetrics and Gynecology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.,Department of Laboratory Medicine, National University Hospital, Singapore, Singapore
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17
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Tabolacci E, Nobile V, Pucci C, Chiurazzi P. Mechanisms of the FMR1 Repeat Instability: How Does the CGG Sequence Expand? Int J Mol Sci 2022; 23:ijms23105425. [PMID: 35628235 PMCID: PMC9141726 DOI: 10.3390/ijms23105425] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2022] [Revised: 05/10/2022] [Accepted: 05/11/2022] [Indexed: 11/16/2022] Open
Abstract
A dynamic mutation in exon 1 of the FMR1 gene causes Fragile X-related Disorders (FXDs), due to the expansion of an unstable CGG repeat sequence. Based on the CGG sequence size, two types of FMR1 alleles are possible: “premutation” (PM, with 56-200 CGGs) and “full mutation” (FM, with >200 triplets). Premutated females are at risk of transmitting a FM allele that, when methylated, epigenetically silences FMR1 and causes Fragile X syndrome (FXS), a very common form of inherited intellectual disability (ID). Expansions events of the CGG sequence are predominant over contractions and are responsible for meiotic and mitotic instability. The CGG repeat usually includes one or more AGG interspersed triplets that influence allele stability and the risk of transmitting FM to children through maternal meiosis. A unique mechanism responsible for repeat instability has not been identified, but several processes are under investigations using cellular and animal models. The formation of unusual secondary DNA structures at the expanded repeats are likely to occur and contribute to the CGG expansion. This review will focus on the current knowledge about CGG repeat instability addressing the CGG sequence expands.
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Affiliation(s)
- Elisabetta Tabolacci
- Dipartimento Scienze della Vita e Sanità Pubblica, Sezione di Medicina Genomica, Università Cattolica del Sacro Cuore, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy; (E.T.); (V.N.); (C.P.)
| | - Veronica Nobile
- Dipartimento Scienze della Vita e Sanità Pubblica, Sezione di Medicina Genomica, Università Cattolica del Sacro Cuore, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy; (E.T.); (V.N.); (C.P.)
| | - Cecilia Pucci
- Dipartimento Scienze della Vita e Sanità Pubblica, Sezione di Medicina Genomica, Università Cattolica del Sacro Cuore, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy; (E.T.); (V.N.); (C.P.)
| | - Pietro Chiurazzi
- Dipartimento Scienze della Vita e Sanità Pubblica, Sezione di Medicina Genomica, Università Cattolica del Sacro Cuore, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy; (E.T.); (V.N.); (C.P.)
- UOC Genetica Medica, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy
- Correspondence: ; Tel.: +39-06-3015-4606
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18
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Barbé L, Finkbeiner S. Genetic and Epigenetic Interplay Define Disease Onset and Severity in Repeat Diseases. Front Aging Neurosci 2022; 14:750629. [PMID: 35592702 PMCID: PMC9110800 DOI: 10.3389/fnagi.2022.750629] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 03/01/2022] [Indexed: 11/13/2022] Open
Abstract
Repeat diseases, such as fragile X syndrome, myotonic dystrophy, Friedreich ataxia, Huntington disease, spinocerebellar ataxias, and some forms of amyotrophic lateral sclerosis, are caused by repetitive DNA sequences that are expanded in affected individuals. The age at which an individual begins to experience symptoms, and the severity of disease, are partially determined by the size of the repeat. However, the epigenetic state of the area in and around the repeat also plays an important role in determining the age of disease onset and the rate of disease progression. Many repeat diseases share a common epigenetic pattern of increased methylation at CpG islands near the repeat region. CpG islands are CG-rich sequences that are tightly regulated by methylation and are often found at gene enhancer or insulator elements in the genome. Methylation of CpG islands can inhibit binding of the transcriptional regulator CTCF, resulting in a closed chromatin state and gene down regulation. The downregulation of these genes leads to some disease-specific symptoms. Additionally, a genetic and epigenetic interplay is suggested by an effect of methylation on repeat instability, a hallmark of large repeat expansions that leads to increasing disease severity in successive generations. In this review, we will discuss the common epigenetic patterns shared across repeat diseases, how the genetics and epigenetics interact, and how this could be involved in disease manifestation. We also discuss the currently available stem cell and mouse models, which frequently do not recapitulate epigenetic patterns observed in human disease, and propose alternative strategies to study the role of epigenetics in repeat diseases.
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Affiliation(s)
- Lise Barbé
- Center for Systems and Therapeutics, Gladstone Institutes, San Francisco, CA, United States
- Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
- Department of Physiology, University of California, San Francisco, San Francisco, CA, United States
| | - Steve Finkbeiner
- Center for Systems and Therapeutics, Gladstone Institutes, San Francisco, CA, United States
- Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
- Department of Physiology, University of California, San Francisco, San Francisco, CA, United States
- *Correspondence: Steve Finkbeiner,
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19
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Meraj N, Yasin M, Rehman ZU, Tahir H, Jadoon H, Khan N, Shahid R, Zubair M, Zulfiqar I, Jabeen M, Neelam S, Hameed A, Saleha S. Fragile X premutation carrier screening in Pakistani preconception women in primary care consultation. BMC Womens Health 2022; 22:57. [PMID: 35246105 PMCID: PMC8895653 DOI: 10.1186/s12905-022-01632-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Accepted: 02/18/2022] [Indexed: 11/24/2022] Open
Abstract
Purpose Women of reproductive age who carry fragile X premutation (PM) alleles have 56 to 200 CGG repeats in the 5′-untranslated region of FMR1 gene are at increased risk for producing children with intellectual disabilities (ID) or autism spectrum disorders (ASD) due to expansion of PM alleles to full mutation alleles (> 200 repeats) during maternal transmission. Methods In present study fragile X PM carrier screening was performed in total 808 women who were consulting primary health care centers for preconception care in Khyber Pakhtunkhwa region of Pakistan between April, 2018 and December, 2020. Polymerase chain reaction (PCR) was performed for detection of PM carrier women and the CGG repeats number was confirmed by Southern blotting and capillary electrophoresis. Results The prevalence rate for PM carriers among preconception women was found to be 0.7% that was contributed by 0.5% women in risk group (RG1) with family history of ID and 0.2% in risk group 2 (RG2) with family history of ASD. PM carrier women had at least one affected child or sibling. In addition, the preconception women with FMR1 PM alleles were found to be at increased risk for primary ovary insufficiency (RG1: P = 0.0265, RG2: P = 0.0389), postpartum depression (RG1: P = 0.0240, RG2: P = 0.0501) and neuropsychiatric disorders (RG1: P = 0.0389, RG2: P = 0.0432). Conclusions Current study provides first evidence of fragile X PM carrier screening in Pakistani preconception women in primary care consultation. Findings of current study may help to improve preconception care and to reduce burden of fragile X associated disorders in our population.
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Affiliation(s)
- Neelam Meraj
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology (KUST), Kohat, 26000, Khyber Pakhtunkhwa, Pakistan
| | - Muhammad Yasin
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology (KUST), Kohat, 26000, Khyber Pakhtunkhwa, Pakistan
| | - Zia Ur Rehman
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology (KUST), Kohat, 26000, Khyber Pakhtunkhwa, Pakistan
| | - Haleema Tahir
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology (KUST), Kohat, 26000, Khyber Pakhtunkhwa, Pakistan
| | - Humaira Jadoon
- Department of Obstetrics and Gynecology, Ayub Medical Institute, Abbottabad, 22010, Khyber Pakhtunkhwa, Pakistan
| | - Niamat Khan
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology (KUST), Kohat, 26000, Khyber Pakhtunkhwa, Pakistan
| | - Rabia Shahid
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology (KUST), Kohat, 26000, Khyber Pakhtunkhwa, Pakistan
| | - Maria Zubair
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology (KUST), Kohat, 26000, Khyber Pakhtunkhwa, Pakistan
| | - Irba Zulfiqar
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology (KUST), Kohat, 26000, Khyber Pakhtunkhwa, Pakistan
| | - Musarrat Jabeen
- Department of Obstetrics and Gynecology, Liaqat Memorial Hospital, KIMS, Kohat, 26000, Khyber Pakhtunkhwa, Pakistan
| | - Shahzadi Neelam
- Department of Obstetrics and Gynecology, Qazi Ahmed Medical Complex, Nowshera, 24100, Khyber Pakhtunkhwa, Pakistan
| | - Abdul Hameed
- Institute of Biomedical and Genetic Engineering (IBGE), Islamabad, 44000, Pakistan
| | - Shamim Saleha
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology (KUST), Kohat, 26000, Khyber Pakhtunkhwa, Pakistan.
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20
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Rajan-Babu IS, Phang GP, Law HY, Lee CG, Chong SS. High-Throughput Methylation-Specific Triplet-Primed PCR and Melting Curve Analysis for Selective and Reliable Identification of Actionable FMR1 Genotypes. J Mol Diagn 2022; 24:241-252. [PMID: 35038595 DOI: 10.1016/j.jmoldx.2021.11.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 10/26/2021] [Accepted: 11/23/2021] [Indexed: 11/17/2022] Open
Abstract
Methylated FMR1 full-mutation expansions cause fragile X syndrome. FMR1 premutation carriers are susceptible to other late-onset conditions, and women with premutation are at risk of transmitting a fully expanded FMR1 allele to offspring. Identification of individuals with actionable FMR1 genotypes (full-mutation males and females, and premutation females at risk for primary ovarian insufficiency and/or having fragile X-affected offspring) can enable timely access to intervention services and genetic counseling. This study presents a rapid, first-tier test based on melting curve analysis of methylation-specific triplet-primed PCR amplicons (msTP-PCR MCA) for concurrent detection of FMR1 CGG-repeat expansions and their methylation status. The msTP-PCR MCA assay was optimized on 20 fragile X reference samples, and its performance was evaluated on 111 peripheral blood-derived DNA samples from patients who have undergone prior molecular testing with PCR and/or Southern blot analysis. The msTP-PCR MCA assay detected all samples with a methylated FMR1 CGG-repeat expansion, and had sensitivity, specificity, positive predictive value, and negative predictive values of 100%, 92.06%, 91.1%, and 100%, respectively. The msTP-PCR MCA assay identified premutation/full-mutation mosaicism down to 1%, detected skewed inactivation in females with FMR1 expansions, and enabled selective identification of all individuals with an actionable FMR1 genotype. The msTP-PCR MCA assay may aid in fragile X screening of at-risk populations and newborns and voluntary carrier screening of women of reproductive age.
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Affiliation(s)
- Indhu-Shree Rajan-Babu
- Department of Pediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Department of Medical Genetics, University of British Columbia, and Children's and Women's Hospital, Vancouver, British Columbia, Canada.
| | - Gui-Ping Phang
- Department of Pediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Hai-Yang Law
- Department of Pediatric Medicine, KK Women's and Children's Hospital, Singapore
| | - Caroline G Lee
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Division of Cellular and Molecular Research, Humphrey Oei Institute of Cancer Research, National Cancer Centre Singapore, Singapore; Cancer and Stem Cell Biology Program, Duke-NUS Medical School, Singapore
| | - Samuel S Chong
- Department of Pediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Department of Obstetrics and Gynecology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Department of Laboratory Medicine, National University Hospital, Singapore.
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21
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Behavior Problems and Social Competence in Fragile X Syndrome: A Systematic Review. Genes (Basel) 2022; 13:genes13020280. [PMID: 35205326 PMCID: PMC8871871 DOI: 10.3390/genes13020280] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 01/27/2022] [Accepted: 01/28/2022] [Indexed: 02/06/2023] Open
Abstract
Fragile X syndrome (FXS) causes intellectual disability and is the known leading cause of autism. Common problems in FXS include behavior and social problems. Along with syndromic characteristics and autism comorbidity, environmental factors might influence these difficulties. This systematic review focuses on the last 20 years of studies concerning behavior and social problems in FXS, considering environmental and personal variables that might influence both problems. Three databases were reviewed, leading to fifty-one studies meeting the inclusion criteria. Attention deficit hyperactivity disorder (ADHD) problems remain the greatest behavior problems, with behavioral problems and social competence being stable during the 20 years. Some developmental trajectories might have changed due to higher methodological control, such as aggressive behavior and attention problems. The socialization trajectory from childhood to adolescence remains unclear. Comorbidity with autism in individuals with FXS increased behavior problems and worsened social competence profiles. At the same time, comparisons between individuals with comorbid FXS and autism and individuals with autism might help define the comorbid phenotype. Environmental factors and parental characteristics influenced behavior problems and social competence. Higher methodological control is needed in studies including autism symptomatology and parental characteristics. More studies comparing autism in FXS with idiopathic autism are needed to discern differences between conditions.
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22
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Annear DJ, Vandeweyer G, Sanchis-Juan A, Raymond FL, Kooy RF. Non-Mendelian inheritance patterns and extreme deviation rates of CGG repeats in autism. Genome Res 2022; 32:1967-1980. [PMID: 36351771 PMCID: PMC9808627 DOI: 10.1101/gr.277011.122] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Accepted: 10/14/2022] [Indexed: 11/10/2022]
Abstract
As expansions of CGG short tandem repeats (STRs) are established as the genetic etiology of many neurodevelopmental disorders, we aimed to elucidate the inheritance patterns and role of CGG STRs in autism-spectrum disorder (ASD). By genotyping 6063 CGG STR loci in a large cohort of trios and quads with an ASD-affected proband, we determined an unprecedented rate of CGG repeat length deviation across a single generation. Although the concept of repeat length being linked to deviation rate was solidified, we show how shorter STRs display greater degrees of size variation. We observed that CGG STRs did not segregate by Mendelian principles but with a bias against longer repeats, which appeared to magnify as repeat length increased. Through logistic regression, we identified 19 genes that displayed significantly higher rates and degrees of CGG STR expansion within the ASD-affected probands (P < 1 × 10-5). This study not only highlights novel repeat expansions that may play a role in ASD but also reinforces the hypothesis that CGG STRs are specifically linked to human cognition.
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Affiliation(s)
- Dale J. Annear
- Department of Medical Genetics, University of Antwerp, 2600 Antwerp, Belgium
| | - Geert Vandeweyer
- Department of Medical Genetics, University of Antwerp, 2600 Antwerp, Belgium
| | - Alba Sanchis-Juan
- NIHR BioResource, Cambridge University Hospitals NHS Foundation Trust, Cambridge Biomedical Campus, Cambridge, CB2 0QQ, United Kingdom;,Department of Haematology, University of Cambridge, NHS Blood and Transplant Centre, Cambridge, CB2 0PT, United Kingdom
| | - F. Lucy Raymond
- NIHR BioResource, Cambridge University Hospitals NHS Foundation Trust, Cambridge Biomedical Campus, Cambridge, CB2 0QQ, United Kingdom;,Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, CB2 0XY, United Kingdom
| | - R. Frank Kooy
- Department of Medical Genetics, University of Antwerp, 2600 Antwerp, Belgium
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Hnoonual A, Jankittunpaiboon C, Limprasert P. Screening for FMR1 CGG Repeat Expansion in Thai Patients with Autism Spectrum Disorder. BIOMED RESEARCH INTERNATIONAL 2021; 2021:4359308. [PMID: 34926684 PMCID: PMC8674057 DOI: 10.1155/2021/4359308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 11/07/2021] [Accepted: 11/26/2021] [Indexed: 11/30/2022]
Abstract
Autism spectrum disorder (ASD) is a complex disorder with a heterogeneous etiology. Fragile X syndrome (FXS) is recognized as the most common single gene mutation associated with ASD. FXS patients show some autistic behaviors and may be difficult to distinguish at a young age from autistic children. However, there have been no published reports on the prevalence of FXS in ASD patients in Thailand. In this study, we present a pilot study to analyze the CGG repeat sizes of the FMR1 gene in Thai autistic patients. We screened 202 unrelated Thai patients (168 males and 34 females) with nonsyndromic ASD and 212 normal controls using standard FXS molecular diagnosis techniques. The distributions of FMR1 CGG repeat sizes in the ASD and normal control groups were similar, with the two most common alleles having 29 and 30 CGG repeats, followed by an allele with 36 CGG repeats. No FMR1 full mutations or premutations were found in either ASD individuals or the normal controls. Interestingly, three ASD male patients with high normal CGG and intermediate CGG repeats (44, 46, and 53 CGG repeats) were identified, indicating that the prevalence of FMR1 intermediate alleles in Thai ASD patients was approximately 1% while these alleles were absent in the normal male controls. Our study indicates that CGG repeat expansions of the FMR1 gene may not be a common genetic cause of nonsyndromic ASD in Thai patients. However, further studies for mutations other than the CGG expansion in the FMR1 gene are required to get a better information on FXS prevalence in Thai ASD patients.
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Affiliation(s)
- Areerat Hnoonual
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla 90110, Thailand
| | | | - Pornprot Limprasert
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla 90110, Thailand
- Faculty of Medicine, Siam University, Bangkok 10160, Thailand
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Frequency of FMR1 Premutation Alleles in Patients with Undiagnosed Cerebellar Ataxia and Multiple System Atrophy in the Japanese Population. CEREBELLUM (LONDON, ENGLAND) 2021; 21:954-962. [PMID: 34845661 DOI: 10.1007/s12311-021-01329-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 09/26/2021] [Indexed: 10/19/2022]
Abstract
Fragile X-associated tremor/ataxia syndrome (FXTAS) is an adult-onset neurodegenerative disorder caused by FMR1 premutation expansion of CGG repeats. FXTAS can be misdiagnosed with many neurodegenerative disorders manifesting with cerebellar ataxias owing to their overlapping clinical and radiological features. The frequency of the FMR1 premutation allele in Japan has not been fully determined. Herein, we aimed to determine the frequency of FMR1 premutation alleles in Japanese patients with undiagnosed cerebellar ataxia and multiple system atrophy, using repeat-primed PCR in 186 patients with adult onset of undiagnosed cerebellar ataxia and 668 patients with multiple system atrophy, to identify expanded CGG repeats as well as to detect AGG interruptions within the expanded alleles. The size of expansions was estimated using fragment length analysis of PCR products obtained by conventional PCR employing a pair of unique primers flanking the repeat sequence. We identified FMR1 premutation alleles in three male patients. One patient revealed 84 repeat units with one AGG interruption and another patient showed 103 repeat units. Both had presented with sporadic cerebellar ataxia, giving an estimated frequency of 3.7% among Japanese male patients with sporadic cerebellar ataxia with age at onset above 50 years. One patient with the clinical diagnosis of multiple system atrophy harbored 60 repeat units with four AGG interruptions. FMR1 intermediate alleles were observed in two males and one female among the multiple system atrophy patients. We found that genetic tests for FMR1 premutation should be considered in Japanese male patients with cerebellar ataxia with the age at onset above 50 years.
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Grosso V, Marcolungo L, Maestri S, Alfano M, Lavezzari D, Iadarola B, Salviati A, Mariotti B, Botta A, D’Apice MR, Novelli G, Delledonne M, Rossato M. Characterization of FMR1 Repeat Expansion and Intragenic Variants by Indirect Sequence Capture. Front Genet 2021; 12:743230. [PMID: 34646309 PMCID: PMC8504923 DOI: 10.3389/fgene.2021.743230] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2021] [Accepted: 08/26/2021] [Indexed: 11/30/2022] Open
Abstract
Traditional methods for the analysis of repeat expansions, which underlie genetic disorders, such as fragile X syndrome (FXS), lack single-nucleotide resolution in repeat analysis and the ability to characterize causative variants outside the repeat array. These drawbacks can be overcome by long-read and short-read sequencing, respectively. However, the routine application of next-generation sequencing in the clinic requires target enrichment, and none of the available methods allows parallel analysis of long-DNA fragments using both sequencing technologies. In this study, we investigated the use of indirect sequence capture (Xdrop technology) coupled to Nanopore and Illumina sequencing to characterize FMR1, the gene responsible of FXS. We achieved the efficient enrichment (> 200×) of large target DNA fragments (~60-80 kbp) encompassing the entire FMR1 gene. The analysis of Xdrop-enriched samples by Nanopore long-read sequencing allowed the complete characterization of repeat lengths in samples with normal, pre-mutation, and full mutation status (> 1 kbp), and correctly identified repeat interruptions relevant for disease prognosis and transmission. Single-nucleotide variants (SNVs) and small insertions/deletions (indels) could be detected in the same samples by Illumina short-read sequencing, completing the mutational testing through the identification of pathogenic variants within the FMR1 gene, when no typical CGG repeat expansion is detected. The study successfully demonstrated the parallel analysis of repeat expansions and SNVs/indels in the FMR1 gene at single-nucleotide resolution by combining Xdrop enrichment with two next-generation sequencing approaches. With the appropriate optimization necessary for the clinical settings, the system could facilitate both the study of genotype-phenotype correlation in FXS and enable a more efficient diagnosis and genetic counseling for patients and their relatives.
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Affiliation(s)
- Valentina Grosso
- Department of Biotechnology, University of Verona, Verona, Italy
| | - Luca Marcolungo
- Department of Biotechnology, University of Verona, Verona, Italy
| | - Simone Maestri
- Department of Biotechnology, University of Verona, Verona, Italy
| | | | - Denise Lavezzari
- Department of Biotechnology, University of Verona, Verona, Italy
| | - Barbara Iadarola
- Department of Biotechnology, University of Verona, Verona, Italy
| | - Alessandro Salviati
- Department of Biotechnology, University of Verona, Verona, Italy
- GENARTIS srl, Verona, Italy
| | - Barbara Mariotti
- Department of Medicine, Section of General Pathology, University of Verona, Verona, Italy
| | - Annalisa Botta
- Department of Biomedicine and Prevention, Medical Genetics Section, University of Rome "Tor Vergata", Rome, Italy
| | | | - Giuseppe Novelli
- Department of Biomedicine and Prevention, Medical Genetics Section, University of Rome "Tor Vergata", Rome, Italy
- IRCCS Neuromed Mediterranean Neurological Institute, Pozzilli, Italy
- Department of Pharmacology, School of Medicine, University of Nevada, Reno, NV, United States
| | - Massimo Delledonne
- Department of Biotechnology, University of Verona, Verona, Italy
- GENARTIS srl, Verona, Italy
| | - Marzia Rossato
- Department of Biotechnology, University of Verona, Verona, Italy
- GENARTIS srl, Verona, Italy
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Rosario R, Anderson R. The molecular mechanisms that underlie fragile X-associated premature ovarian insufficiency: is it RNA or protein based? Mol Hum Reprod 2021; 26:727-737. [PMID: 32777047 PMCID: PMC7566375 DOI: 10.1093/molehr/gaaa057] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 08/03/2020] [Indexed: 01/30/2023] Open
Abstract
The FMR1 gene contains a polymorphic CGG trinucleotide sequence within its 5′ untranslated region. More than 200 CGG repeats (termed a full mutation) underlie the severe neurodevelopmental condition fragile X syndrome, while repeat lengths that range between 55 and 200 (termed a premutation) result in the conditions fragile X-associated tremor/ataxia syndrome and fragile X-associated premature ovarian insufficiency (FXPOI). Premutations in FMR1 are the most common monogenic cause of premature ovarian insufficiency and are routinely tested for clinically; however, the mechanisms that contribute to the pathology are still largely unclear. As studies in this field move towards unravelling the molecular mechanisms involved in FXPOI aetiology, we review the evidence surrounding the two main theories which describe an RNA toxic gain-of-function mechanism, resulting in the loss of function of RNA-binding proteins, or a protein-based mechanism, where repeat-associated non-AUG translation leads to the formation of an abnormal polyglycine containing protein, called FMRpolyG.
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Affiliation(s)
- Roseanne Rosario
- MRC Centre for Reproductive Health, Queens Medical Research Institute, University of Edinburgh, Edinburgh, UK
| | - Richard Anderson
- MRC Centre for Reproductive Health, Queens Medical Research Institute, University of Edinburgh, Edinburgh, UK
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Fyke W, Velinov M. FMR1 and Autism, an Intriguing Connection Revisited. Genes (Basel) 2021; 12:genes12081218. [PMID: 34440392 PMCID: PMC8394635 DOI: 10.3390/genes12081218] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 08/03/2021] [Accepted: 08/04/2021] [Indexed: 12/27/2022] Open
Abstract
Autism Spectrum Disorder (ASD) represents a distinct phenotype of behavioral dysfunction that includes deficiencies in communication and stereotypic behaviors. ASD affects about 2% of the US population. It is a highly heritable spectrum of conditions with substantial genetic heterogeneity. To date, mutations in over 100 genes have been reported in association with ASD phenotypes. Fragile X syndrome (FXS) is the most common single-gene disorder associated with ASD. The gene associated with FXS, FMR1 is located on chromosome X. Accordingly, the condition has more severe manifestations in males. FXS results from the loss of function of FMR1 due to the expansion of an unstable CGG repeat located in the 5'' untranslated region of the gene. About 50% of the FXS males and 20% of the FXS females meet the Diagnostic Statistical Manual 5 (DSM-5) criteria for ASD. Among the individuals with ASD, about 3% test positive for FXS. FMRP, the protein product of FMR1, is a major gene regulator in the central nervous system. Multiple pathways regulated by FMRP are found to be dysfunctional in ASD patients who do not have FXS. Thus, FXS presents the opportunity to study cellular phenomena that may have wider applications in the management of ASD and to develop new strategies for ASD therapy.
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Affiliation(s)
- William Fyke
- SUNY Downstate Medical Center, SUNY Downstate College of Medicine, Brooklyn, NY 11203, USA;
- Graduate Program in Neural and Behavioral Science, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
| | - Milen Velinov
- Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ 08901, USA
- Child Health Institute of New Jersey, New Brunswick, NJ 08901, USA
- Correspondence:
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28
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Xi H, Xie W, Chen J, Tang W, Deng X, Li H, Peng Y, Wang D, Yang S, Zhang Y, Duan R, Fang J, Wang H. Implementation of fragile X syndrome carrier screening during prenatal diagnosis: A pilot study at a single center. Mol Genet Genomic Med 2021; 9:e1711. [PMID: 34057320 PMCID: PMC8372084 DOI: 10.1002/mgg3.1711] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 04/15/2021] [Accepted: 04/30/2021] [Indexed: 12/02/2022] Open
Abstract
Background Fragile X syndrome (FXS) is the most common inherited form of intellectual disability. Prenatal screening of FXS allows for early identification and intervention. The present study explored the feasibility of FXS carrier screening during prenatal diagnosis for those who were not offered screening early in pregnancy or prior to conception. Methods Pregnant women to be offered amniotic fluid testing were recruited for the free voluntary carrier screening at a single center between August, 2017 and September, 2019. The number of CGG repeats in the 5’ un‐translated region of the fragile X mental retardation gene 1 (FMR1) was determined. Results 4286 of 7000 (61.2%) pregnant women volunteered for the screening. Forty (0.93%), five (0.11%), and three (0.07%) carriers for intermediate mutation (45–54 repeats), premutation (55–200 repeats) and full mutation (>200 repeats) of the FMR1 gene were identified respectively. None of the detected premutation alleles were inherited by the fetuses. Of the three full mutation carrier mothers, all had a family history and one transmitted a full mutation allele to her male fetus. Conclusion Implementation of FXS carrier screening during prenatal diagnosis may be considered for the need to increase screening for FXS.
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Affiliation(s)
- Hui Xi
- Department of Medical Genetics & the Prenatal Diagnosis Center of Hunan Province, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China.,NHC Key Laboratory of Birth Defects for Research and Prevention, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China
| | - Wanqin Xie
- NHC Key Laboratory of Birth Defects for Research and Prevention, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China
| | - Jing Chen
- Department of Medical Genetics & the Prenatal Diagnosis Center of Hunan Province, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China
| | - Wanglan Tang
- Department of Medical Genetics & the Prenatal Diagnosis Center of Hunan Province, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China
| | - Xiuli Deng
- Department of Medical Genetics & the Prenatal Diagnosis Center of Hunan Province, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China
| | - Hua Li
- Department of Medical Genetics & the Prenatal Diagnosis Center of Hunan Province, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China
| | - Ying Peng
- Department of Medical Genetics & the Prenatal Diagnosis Center of Hunan Province, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China.,NHC Key Laboratory of Birth Defects for Research and Prevention, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China
| | - Dan Wang
- Department of Medical Genetics & the Prenatal Diagnosis Center of Hunan Province, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China
| | - Shuting Yang
- Department of Medical Genetics & the Prenatal Diagnosis Center of Hunan Province, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China
| | - Yanan Zhang
- Department of Medical Genetics & the Prenatal Diagnosis Center of Hunan Province, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China
| | - Ranhui Duan
- Center for Medical Genetics, School of Life Sciences & Hunan Key Laboratory of Medical Genetics, Central South University, Changsha, Hunan, China
| | - Junqun Fang
- Department of Health Care, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China
| | - Hua Wang
- Department of Medical Genetics & the Prenatal Diagnosis Center of Hunan Province, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China.,NHC Key Laboratory of Birth Defects for Research and Prevention, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China
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Nolin SL, Napoli E, Flores A, Hagerman RJ, Giulivi C. Deficits in Prenatal Serine Biosynthesis Underlie the Mitochondrial Dysfunction Associated with the Autism-Linked FMR1 Gene. Int J Mol Sci 2021; 22:ijms22115886. [PMID: 34070950 PMCID: PMC8198117 DOI: 10.3390/ijms22115886] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Revised: 05/25/2021] [Accepted: 05/27/2021] [Indexed: 12/22/2022] Open
Abstract
Fifty-five to two hundred CGG repeats (called a premutation, or PM) in the 5′-UTR of the FMR1 gene are generally unstable, often expanding to a full mutation (>200) in one generation through maternal inheritance, leading to fragile X syndrome, a condition associated with autism and other intellectual disabilities. To uncover the early mechanisms of pathogenesis, we performed metabolomics and proteomics on amniotic fluids from PM carriers, pregnant with male fetuses, who had undergone amniocentesis for fragile X prenatal diagnosis. The prenatal metabolic footprint identified mitochondrial deficits, which were further validated by using internal and external cohorts. Deficits in the anaplerosis of the Krebs cycle were noted at the level of serine biosynthesis, which was confirmed by rescuing the mitochondrial dysfunction in the carriers’ umbilical cord fibroblasts using alpha-ketoglutarate precursors. Maternal administration of serine and its precursors has the potential to decrease the risk of developing energy shortages associated with mitochondrial dysfunction and linked comorbidities.
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Affiliation(s)
- Sarah L. Nolin
- Department of Human Genetics, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, NY 10314, USA;
| | - Eleonora Napoli
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA; (E.N.); (A.F.)
| | - Amanda Flores
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA; (E.N.); (A.F.)
- Medical Sciences Campus, Department of Biochemistry, University of Puerto Rico, San Juan PR00936, Puerto Rico
| | - Randi J. Hagerman
- Department of Pediatrics, University of California Davis Medical Center, Sacramento, CA 95817, USA;
- The MIND Institute, University of California Davis Medical Center, Sacramento, CA 95817, USA
| | - Cecilia Giulivi
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA; (E.N.); (A.F.)
- The MIND Institute, University of California Davis Medical Center, Sacramento, CA 95817, USA
- Correspondence: ; Tel.: +1-530-754-8603
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30
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Detection of Cryptic Fragile X Full Mutation Alleles by Southern Blot in a Female and Her Foetal DNA via Chorionic Villus Sampling, Complicated by Mosaicism for 45,X0/46,XX/47,XXX. Genes (Basel) 2021; 12:genes12060798. [PMID: 34073864 PMCID: PMC8225079 DOI: 10.3390/genes12060798] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 05/08/2021] [Accepted: 05/18/2021] [Indexed: 11/23/2022] Open
Abstract
We describe a female with a 72 CGG FMR1 premutation (PM) (CGG 55–199) and family history of fragile X syndrome (FXS), referred for prenatal testing. The proband had a high risk of having an affected pregnancy with a full mutation allele (FM) (CGG > 200), that causes FXS through hypermethylation of the FMR1 promoter. The CGG sizing analysis in this study used AmplideX triplet repeat primed polymerase chain reaction (TP-PCR) and long-range methylation sensitive PCR (mPCR). These methods detected a 73 CGG PM allele in the proband’s blood, and a 164 CGG PM allele in her male cultured chorionic villus sample (CVS). In contrast, the Southern blot analysis showed mosaicism for: (i) a PM (71 CGG) and an FM (285–768 CGG) in the proband’s blood, and (ii) a PM (165 CGG) and an FM (408–625 CGG) in the male CVS. The FMR1 methylation analysis, using an EpiTYPER system in the proband, showed levels in the range observed for mosaic Turner syndrome. This was confirmed by molecular and cytogenetic karyotyping, identifying 45,X0/46,XX/47,XXX lines. In conclusion, this case highlights the importance of Southern blot in pre- and postnatal testing for presence of an FM, which was not detected using AmplideX TP-PCR or mPCR in the proband and her CVS.
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Laboratory testing for fragile X, 2021 revision: a technical standard of the American College of Medical Genetics and Genomics (ACMG). Genet Med 2021; 23:799-812. [PMID: 33795824 DOI: 10.1038/s41436-021-01115-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 02/01/2021] [Accepted: 02/02/2021] [Indexed: 11/08/2022] Open
Abstract
Molecular genetic testing of the FMR1 gene is commonly performed in clinical laboratories. Pathogenic variants in the FMR1 gene are associated with fragile X syndrome, fragile X-associated tremor ataxia syndrome (FXTAS), and fragile X-associated primary ovarian insufficiency (FXPOI). This document provides updated information regarding FMR1 pathogenic variants, including prevalence, genotype-phenotype correlations, and variant nomenclature. Methodological considerations are provided for Southern blot analysis and polymerase chain reaction (PCR) amplification of FMR1, including triplet repeat-primed and methylation-specific PCR.The American College of Medical Genetics and Genomics (ACMG) Laboratory Quality Assurance Committee has the mission of maintaining high technical standards for the performance and interpretation of genetic tests. In part, this is accomplished by the publication of the document ACMG Technical Standards for Clinical Genetics Laboratories, which is now maintained online ( http://www.acmg.net ). This subcommittee also reviews the outcome of national proficiency testing in the genetics area and may choose to focus on specific diseases or methodologies in response to those results. Accordingly, the subcommittee selected fragile X syndrome to be the first topic in a series of supplemental sections, recognizing that it is one of the most frequently ordered genetic tests and that it has many alternative methods with different strengths and weaknesses. This document is the fourth update to the original standards and guidelines for fragile X testing that were published in 2001, with revisions in 2005 and 2013, respectively.This versionClarifies the clinical features associated with different FMRI variants (Section 2.3)Discusses important reporting considerations (Section 3.3.1.3)Provides updates on technology (Section 4.1).
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Sui Y, Peng S. A Mechanism Leading to Changes in Copy Number Variations Affected by Transcriptional Level Might Be Involved in Evolution, Embryonic Development, Senescence, and Oncogenesis Mediated by Retrotransposons. Front Cell Dev Biol 2021; 9:618113. [PMID: 33644055 PMCID: PMC7905054 DOI: 10.3389/fcell.2021.618113] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 01/11/2021] [Indexed: 01/05/2023] Open
Abstract
In recent years, more and more evidence has emerged showing that changes in copy number variations (CNVs) correlated with the transcriptional level can be found during evolution, embryonic development, and oncogenesis. However, the underlying mechanisms remain largely unknown. The success of the induced pluripotent stem cell suggests that genome changes could bring about transformations in protein expression and cell status; conversely, genome alterations generated during embryonic development and senescence might also be the result of genome changes. With rapid developments in science and technology, evidence of changes in the genome affected by transcriptional level has gradually been revealed, and a rational and concrete explanation is needed. Given the preference of the HIV-1 genome to insert into transposons of genes with high transcriptional levels, we propose a mechanism based on retrotransposons facilitated by specific pre-mRNA splicing style and homologous recombination (HR) to explain changes in CNVs in the genome. This mechanism is similar to that of the group II intron that originated much earlier. Under this proposed mechanism, CNVs on genome are dynamically and spontaneously extended in a manner that is positively correlated with transcriptional level or contract as the cell divides during evolution, embryonic development, senescence, and oncogenesis, propelling alterations in them. Besides, this mechanism explains several critical puzzles in these processes. From evidence collected to date, it can be deduced that the message contained in genome is not just three-dimensional but will become four-dimensional, carrying more genetic information.
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Affiliation(s)
- Yunpeng Sui
- Department of Functional Neurosurgery, Beijing Neurosurgical Institute, Capital Medical University, Beijing, China
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Nakayama Y, Adachi K, Shioda N, Maeta S, Nanba E, Kugoh H. Establishment of FXS-A9 panel with a single human X chromosome from fragile X syndrome-associated individual. Exp Cell Res 2020; 398:112419. [PMID: 33296661 DOI: 10.1016/j.yexcr.2020.112419] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2020] [Revised: 11/20/2020] [Accepted: 11/26/2020] [Indexed: 11/29/2022]
Abstract
Fragile X syndrome (FXS) is the most common inheritable form of intellectual disability. FMR1, the gene responsible for FXS, is located on human chromosome Xq27.3 and contains a stretch of CGG trinucleotide repeats in its 5' untranslated region. FXS is caused by CGG repeats that expand beyond 200, resulting in FMR1 silencing via promoter hypermethylation. The molecular mechanism underlying CGG repeat expansion, a fundamental cause of FXS, remains poorly understood, partly due to a lack of experimental systems. Accumulated evidence indicates that the large chromosomal region flanking a CGG repeat is critical for repeat dynamics. In the present study, we isolated and introduced whole human X chromosomes from healthy, FXS premutation carriers, or FXS patients who carried disease condition-associated CGG repeat lengths, into mouse A9 cells via microcell-mediated chromosome transfer. The CGG repeat length-associated methylation status and human FMR1 expression in these monochromosomal hybrid cells mimicked those in humans. Thus, this set of A9 cells containing CGG repeats from three different origins (FXS-A9 panel) may provide a valuable resource for investigating a series of genetic and epigenetic CGG repeat dynamics during FXS pathogenesis.
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Affiliation(s)
- Yuji Nakayama
- Division of Radioisotope Science, Research Initiative Center, Organization for Research Initiative and Promotion, Tottori University, 86 Nishi-cho, Yonago, Tottori, 683-8503, Japan
| | - Kaori Adachi
- Division of Genomic Science, Research Initiative Center, Organization for Research Initiative and Promotion, Tottori University, 86 Nishi-cho, Yonago, Tottori, 683-8503, Japan
| | - Nofirifumi Shioda
- Department of Genomic Neurology, Institute of Molecular Embryology and Genetics, Kumamoto University, 2-2-1 Honjo, Chuo-ku, Kumamoto, 860-0811, Japan
| | - Shoya Maeta
- Department of Biomedical Science, Institute of Regenerative Medicine and Biofunction, Graduate School of Medical Science, Tottori University, 86 Nishi-cho, Yonago, Tottori, 683-8503, Japan
| | - Eiji Nanba
- Office for Research Strategy, Organization for Research Initiative and Promotion, Tottori University, 86 Nishi-cho, Yonago, Tottori, 683-8503, Japan
| | - Hiroyuki Kugoh
- Department of Biomedical Science, Institute of Regenerative Medicine and Biofunction, Graduate School of Medical Science, Tottori University, 86 Nishi-cho, Yonago, Tottori, 683-8503, Japan; Chromosome Engineering Research Center, Tottori University, 86 Nishi-cho, Yonago, Tottori, 683-8503, Japan.
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Villate O, Ibarluzea N, Maortua H, de la Hoz AB, Rodriguez-Revenga L, Izquierdo-Álvarez S, Tejada MI. Effect of AGG Interruptions on FMR1 Maternal Transmissions. Front Mol Biosci 2020; 7:135. [PMID: 32766278 PMCID: PMC7381193 DOI: 10.3389/fmolb.2020.00135] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 06/05/2020] [Indexed: 12/30/2022] Open
Abstract
There are four classes of CGG repeat alleles in the FMR1 gene: normal alleles have up to 44 repeats; patients with Fragile X Syndrome have more than 200 repeats; those between 55 and 200 CGGs are considered FMR1 premutation alleles, because they are associated with maternal expansions of the number of CGGs in the next generation and finally, alleles between 45 and 54 CGGs are called intermediate or gray zone alleles. In these last categories, the stability depends on the presence of AGG interruptions, which usually occurs between 9 and 10 CGGs. In this context, we have studied retrospectively 66 women with CGG repeats between 45 and 65, and their offspring. In total 87 transmissions were analyzed with triplet repeat primed PCR using AmplideX® FMR1 PCR (Asuragen, Austin, TX, USA) and we found that alleles with CGG repeats between 45 and 58 do not expand in the next generation except two cases with 56 repeats and 0 AGG interruptions. Furthermore, we have found four females with alleles with more than 59 CGG repeats and 2 AGG interruptions that do not expand either. Alleles from 56 CGG repeats without AGGs expand in all cases. In light of these results and those of the literature, we consider that the risk of unstable transmissions should be based on the presence or absence of AGG interruptions and not on the classical cutoffs which define each category of FMR1 alleles. The application of these results in the genetic and reproductive counseling is essential and AGG interruptions should always be studied.
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Affiliation(s)
- Olatz Villate
- Biocruces Bizkaia Health Research Institute, Barakaldo, Spain.,Genetics Service, Cruces University Hospital, Osakidetza Basque Health Service, Barakaldo, Spain.,Centre for Biomedical Research on Rare Diseases (CIBERER), ISCIII, Madrid, Spain
| | - Nekane Ibarluzea
- Biocruces Bizkaia Health Research Institute, Barakaldo, Spain.,Centre for Biomedical Research on Rare Diseases (CIBERER), ISCIII, Madrid, Spain
| | - Hiart Maortua
- Genetics Service, Cruces University Hospital, Osakidetza Basque Health Service, Barakaldo, Spain.,Centre for Biomedical Research on Rare Diseases (CIBERER), ISCIII, Madrid, Spain
| | - Ana Belén de la Hoz
- Biocruces Bizkaia Health Research Institute, Barakaldo, Spain.,Centre for Biomedical Research on Rare Diseases (CIBERER), ISCIII, Madrid, Spain
| | - Laia Rodriguez-Revenga
- Centre for Biomedical Research on Rare Diseases (CIBERER), ISCIII, Madrid, Spain.,Biochemistry and Molecular Genetics Department, Hospital Clinic, Barcelona, Spain.,Institut d'Investigació Biomèdica August Pi i Sunyer IDIBAPS, Barcelona, Spain
| | - Silvia Izquierdo-Álvarez
- Genetics Department of Clinical Biochemistry, Hospital Universitario Miguel Servet, Zaragoza, Spain
| | - María Isabel Tejada
- Biocruces Bizkaia Health Research Institute, Barakaldo, Spain.,Genetics Service, Cruces University Hospital, Osakidetza Basque Health Service, Barakaldo, Spain.,Centre for Biomedical Research on Rare Diseases (CIBERER), ISCIII, Madrid, Spain
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35
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An explanation of the mechanisms underlying fragile X-associated premature ovarian insufficiency. J Assist Reprod Genet 2020; 37:1313-1322. [PMID: 32377997 PMCID: PMC7311620 DOI: 10.1007/s10815-020-01774-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Accepted: 04/01/2020] [Indexed: 12/22/2022] Open
Abstract
Fragile X and fragile X-associated tremor-ataxia syndrome (FXTAS) are caused by mutations of the FMR1 gene. The mutations causing FXTAS can expand in a generation to a "full mutation" causing fragile X syndrome. The mutations causing FXTAS and the phenotype, fragile X-associated premature ovarian insufficiency (FXPOI), are referred to as the FMR1 premutation (PM). The objective of this paper was to formulate a theory to explain the Mechanism for FXPOI.Recent research on fragile X syndrome and FXTAS has led to sophisticated theories about the mechanisms underlying these diseases. It has been proposed that similar mechanisms underlie FXPOI. Utilizing recent research on FXTAS, but a more detailed application of ovarian physiology, we present a more ovarian specific theory as to the primary mechanism explaining the development of FXPOI.The FXPOI phenotype may best be viewed as derivative of the observation that fragile X PM carriers experience menopause an average of 5 years earlier than non-carriers. Women carrying the PM experience an earlier menopause because of an accelerated activation of their primordial follicle pool. This acceleration of primordial follicle activation occurs, in part, because of diminished AMH production. AMH production is diminished because of accelerated atresia of early antral follicles. This accelerated atresia likely occurs because the fragile X PM leads to a slowing of the rate of granulosa cell mitosis in some follicles.
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Clinical experience with carrier screening in a general population: support for a comprehensive pan-ethnic approach. Genet Med 2020; 22:1320-1328. [PMID: 32366966 PMCID: PMC7394882 DOI: 10.1038/s41436-020-0807-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 03/31/2020] [Accepted: 04/01/2020] [Indexed: 12/18/2022] Open
Abstract
Purpose To present results from a large cohort of individuals receiving
expanded carrier screening (CS) in the United States. Methods Single-gene disorder carrier status for 381,014 individuals was
determined using next-generation sequencing (NGS) based CS for up to 274 genes.
Detection rates were compared with literature-reported values derived from
disease prevalence and carrier frequencies. Combined theoretical affected
pregnancy rates for the 274 screened disorders were calculated. Results For Ashkenazi Jewish (AJ) diseases, 81.6% (4434/5435) of carriers
identified did not report AJ ancestry. For cystic fibrosis, 44.0% (6260/14,229)
of carriers identified had a variant not on the standard genotyping panel.
Individuals at risk of being a silent spinal muscular atrophy carrier, not
detectable by standard screening, comprised 1/39 (8763/344,407) individuals. For
fragile X syndrome, compared with standard premutation screening, AGG
interruption analysis modified risk in 83.2% (1128/1356) premutation carriers.
Assuming random pairing across the study population, approximately 1/175
pregnancies would be affected by a disorder in the 274-gene screening
panel. Conclusion Compared with standard screening, NGS-based CS provides additional
information that may impact reproductive choices. Pan-ethnic CS leads to
substantially increased identification of at-risk couples. These data support
offering NGS-based CS to all reproductive-aged women.
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Gao F, Huang W, You Y, Huang J, Zhao J, Xue J, Kang H, Zhu Y, Hu Z, Allen EG, Jin P, Xia K, Duan R. Development of Chinese genetic reference panel for Fragile X Syndrome and its application to the screen of 10,000 Chinese pregnant women and women planning pregnancy. Mol Genet Genomic Med 2020; 8:e1236. [PMID: 32281281 PMCID: PMC7284044 DOI: 10.1002/mgg3.1236] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 02/24/2020] [Accepted: 03/01/2020] [Indexed: 02/02/2023] Open
Abstract
Background Fragile X syndrome (FXS) is the most common inherited form of intellectual disability caused by a CGG repeat expansion in the 5′ untranslated region of the FMR1 gene. When the number of repeats exceeds 200, the gene becomes hypermethylated and is transcriptionally silenced, resulting in FXS. Other allelic forms of the gene that are studied because of their instability or phenotypic consequence include intermediate alleles (45–54 CGG repeats) and premutation alleles (55–200 repeats). Normal alleles are classified as having <45 CGG repeats. Population screening studies have been conducted among American and Australian populations; however, large population‐based studies have not been completed in China. Methods and Results In this work we present FXS screening results from 10,145 women of childbearing age from China. We first created and tested a standard panel that was comprised of normal, intermediate, premutation, and full mutation samples, and we performed the screening after confirming the consistency of genotyping results among laboratories. Conclusion Based on our findings, we have determined the intermediate and premutation carrier prevalence of 1/130 and 1/634, respectively, among Chinese women.
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Affiliation(s)
- Fei Gao
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China.,National Institutes for Food and Drug Control, Beijing, China
| | - Wen Huang
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Yanjun You
- National Institutes for Food and Drug Control, Beijing, China
| | - Jie Huang
- National Institutes for Food and Drug Control, Beijing, China
| | - Juan Zhao
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Jin Xue
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Huaixing Kang
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Yingbao Zhu
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Zhengmao Hu
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China.,Hunan Key Laboratory of Medical Genetics, Central South University, Changsha, Hunan, China
| | - Emily G Allen
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA
| | - Peng Jin
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA
| | - Kun Xia
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China.,Hunan Key Laboratory of Medical Genetics, Central South University, Changsha, Hunan, China
| | - Ranhui Duan
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China.,Hunan Key Laboratory of Medical Genetics, Central South University, Changsha, Hunan, China.,Hunan Key Laboratory of Animal Models for Human Diseases, Central South University, Changsha, Hunan, China
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Khristich AN, Mirkin SM. On the wrong DNA track: Molecular mechanisms of repeat-mediated genome instability. J Biol Chem 2020; 295:4134-4170. [PMID: 32060097 PMCID: PMC7105313 DOI: 10.1074/jbc.rev119.007678] [Citation(s) in RCA: 148] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Expansions of simple tandem repeats are responsible for almost 50 human diseases, the majority of which are severe, degenerative, and not currently treatable or preventable. In this review, we first describe the molecular mechanisms of repeat-induced toxicity, which is the connecting link between repeat expansions and pathology. We then survey alternative DNA structures that are formed by expandable repeats and review the evidence that formation of these structures is at the core of repeat instability. Next, we describe the consequences of the presence of long structure-forming repeats at the molecular level: somatic and intergenerational instability, fragility, and repeat-induced mutagenesis. We discuss the reasons for gender bias in intergenerational repeat instability and the tissue specificity of somatic repeat instability. We also review the known pathways in which DNA replication, transcription, DNA repair, and chromatin state interact and thereby promote repeat instability. We then discuss possible reasons for the persistence of disease-causing DNA repeats in the genome. We describe evidence suggesting that these repeats are a payoff for the advantages of having abundant simple-sequence repeats for eukaryotic genome function and evolvability. Finally, we discuss two unresolved fundamental questions: (i) why does repeat behavior differ between model systems and human pedigrees, and (ii) can we use current knowledge on repeat instability mechanisms to cure repeat expansion diseases?
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Affiliation(s)
| | - Sergei M Mirkin
- Department of Biology, Tufts University, Medford, Massachusetts 02155.
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Orr MW, Mao Y, Storz G, Qian SB. Alternative ORFs and small ORFs: shedding light on the dark proteome. Nucleic Acids Res 2020; 48:1029-1042. [PMID: 31504789 DOI: 10.1093/nar/gkz734] [Citation(s) in RCA: 146] [Impact Index Per Article: 36.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 08/03/2019] [Accepted: 08/15/2019] [Indexed: 02/06/2023] Open
Abstract
Traditional annotation of protein-encoding genes relied on assumptions, such as one open reading frame (ORF) encodes one protein and minimal lengths for translated proteins. With the serendipitous discoveries of translated ORFs encoded upstream and downstream of annotated ORFs, from alternative start sites nested within annotated ORFs and from RNAs previously considered noncoding, it is becoming clear that these initial assumptions are incorrect. The findings have led to the realization that genetic information is more densely coded and that the proteome is more complex than previously anticipated. As such, interest in the identification and characterization of the previously ignored 'dark proteome' is increasing, though we note that research in eukaryotes and bacteria has largely progressed in isolation. To bridge this gap and illustrate exciting findings emerging from studies of the dark proteome, we highlight recent advances in both eukaryotic and bacterial cells. We discuss progress in the detection of alternative ORFs as well as in the understanding of functions and the regulation of their expression and posit questions for future work.
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Affiliation(s)
- Mona Wu Orr
- Division of Molecular and Cellular Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA
| | - Yuanhui Mao
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
| | - Gisela Storz
- Division of Molecular and Cellular Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA
| | - Shu-Bing Qian
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
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40
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Cascade Testing for Fragile X Syndrome in a Rural Setting in Cameroon (Sub-Saharan Africa). Genes (Basel) 2020; 11:genes11020136. [PMID: 32012997 PMCID: PMC7074341 DOI: 10.3390/genes11020136] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Revised: 01/13/2020] [Accepted: 01/22/2020] [Indexed: 11/17/2022] Open
Abstract
Fragile X Syndrome (FXS), an X-linked dominant monogenic condition, is the main genetic cause of intellectual disability (ID) and autism spectrum disorder (ASD). FXS is associated with an expansion of CGG repeat sequence in the Fragile X Mental Retardation gene 1 (FMR1) on chromosome X. Following a neuropediatric assessment of two male siblings who presented with signs of FXS that was confirmed with molecular testing, we provided cascade counselling and testing to the extended family. A total of 46 individuals were tested for FXS; among them, 58.70% (n = 27) were females. The mean age was 9.4 (±5) years for children and 45.9 (±15.9) years for adults. Pedigree analysis suggested that the founder of these families was likely a normal transmitting male. Four out of 19 males with clinical ID were confirmed to have a full mutation for FXS, while 14/27 females had a pathologic CGG expansion (>56 CGG repeats) on one of their X chromosomes. Two women with premature menopause were confirmed of being carriers of premutation (91 and 101 CGG repeats). We also identified maternal alleles (91 and 126 CGG repeats) which expanded to a full mutation in their offspring (>200 CGG repeats). This study is a rare report on FXS from Africa and illustrates the case scenario of implementing genetic medicine for a neurogenetic condition in a rural setting.
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Johansen Taber K, Lim-Harashima J, Naemi H, Goldberg J. Fragile X syndrome carrier screening accompanied by genetic consultation has clinical utility in populations beyond those recommended by guidelines. Mol Genet Genomic Med 2019; 7:e1024. [PMID: 31694075 PMCID: PMC6900367 DOI: 10.1002/mgg3.1024] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 08/30/2019] [Accepted: 10/01/2019] [Indexed: 01/12/2023] Open
Abstract
Background Fragile X syndrome (FXS) is the most common inherited form of intellectual disability. Many providers offer preconception or prenatal FXS carrier screening. However, guidelines recommend screening only for those with a family history or undergoing fertility evaluation. Wider screening has been resisted because of concerns about patient understanding of FXS‐associated inheritance patterns and phenotypes. Additionally, the clinical utility has been questioned. Methods We addressed these concerns by analyzing reproductive decision‐making and pregnancy management informed by post‐test genetic consultation among 122 FMR1 premutation carriers identified by expanded carrier screening. Results Sixty‐three percent of those screened met guidelines screening criteria; the remaining 37% did not. Ninety‐eight percent had undergone post‐test genetic consultation. Of respondents screened preconceptionally, 74% reported planning or pursuing actions to reduce the risk of an affected pregnancy; the extent to which couples planned/pursued these actions was not significantly different between those meeting either screening criterion (76%) versus those meeting neither criterion (55%). Of respondents screened prenatally, 41% pursued prenatal diagnostic testing; the extent to which couples pursued prenatal diagnosis was not significantly different between those who met either screening criterion (37%) versus those who met neither criterion (31%). Conclusion These results support the expansion of FXS screening criteria in guidelines.
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Affiliation(s)
| | | | | | - Jim Goldberg
- Myriad Women's Health, South San Francisco, CA, USA
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42
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Hung CC, Lee CN, Wang YC, Chen CL, Lin TK, Su YN, Lin MW, Kang J, Tai YY, Hsu WW, Lin SY. Fragile X syndrome carrier screening in pregnant women in Chinese Han population. Sci Rep 2019; 9:15456. [PMID: 31664061 PMCID: PMC6820721 DOI: 10.1038/s41598-019-51726-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 10/01/2019] [Indexed: 11/09/2022] Open
Abstract
Fragile X syndrome (FXS) is the most frequent genetic cause of intellectual disability (ID). It was previously believed that the FXS prevalence was low in Chinese population, and the cost-efficiency of FXS carrier screening was questioned. This retrospective observational study was conducted between September 2014 and May 2017 to determine the prevalence of FXS carriers in a large Chinese cohort of pregnant women. The FMR1 CGG repeat status was determined in 20,188 pregnant Taiwanese women and we identified 26 women with premutation (PM). The PM allele was transmitted to the fetus in 17 pregnancies (56.6%), and six of 17 expanded to full mutation (FM). One asymptomatic woman had a FM allele with 280 CGG repeats. Prenatal genetic diagnosis of her first fetus revealed a male carrying a FMR1 gene deletion of 5′ UTR and exon 1. Her second fetus was a female carrying a FM allele as well. This is so far the largest study of the FXS carrier screening in Chinese women. The prevalence of premutation allele for FXS in normal asymptomatic Taiwanese women was found to be as high as 0.13% (1 in 777) in this study. The empirical evidence suggests that reproductive FXS carrier screening in Taiwan might be cost-effective.
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Affiliation(s)
| | - Chien-Nan Lee
- Department of Obstetrics and Gynecology, National Taiwan University Hospital, Taipei, Taiwan.,Department of Obstetrics and Gynecology, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Yu-Chu Wang
- Sofiva Genomics Co., Ltd., Taipei, Taiwan.,Institute of Molecular Medicine, College of Medicine, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Chih-Ling Chen
- Department of Obstetrics and Gynecology, National Taiwan University Hospital, Taipei, Taiwan
| | - Tze-Kang Lin
- Sofiva Genomics Co., Ltd., Taipei, Taiwan.,Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Yi-Ning Su
- Sofiva Genomics Co., Ltd., Taipei, Taiwan.,Dianthus Maternal Fetal Medicine Clinic, Taipei, Taiwan
| | - Ming-Wei Lin
- Department of Obstetrics and Gynecology, National Taiwan University Hospital, Taipei, Taiwan
| | - Jessica Kang
- Department of Obstetrics and Gynecology, National Taiwan University Hospital, Taipei, Taiwan
| | - Yi-Yun Tai
- Department of Obstetrics and Gynecology, National Taiwan University Hospital, Taipei, Taiwan
| | - Wen-Wei Hsu
- Department of Obstetrics and Gynecology, National Taiwan University Hospital, Taipei, Taiwan
| | - Shin-Yu Lin
- Department of Obstetrics and Gynecology, National Taiwan University Hospital, Taipei, Taiwan. .,Department of Obstetrics and Gynecology, National Taiwan University College of Medicine, Taipei, Taiwan.
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43
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Kim N. The Interplay between G-quadruplex and Transcription. Curr Med Chem 2019; 26:2898-2917. [PMID: 29284393 PMCID: PMC6026074 DOI: 10.2174/0929867325666171229132619] [Citation(s) in RCA: 83] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2017] [Revised: 11/22/2017] [Accepted: 12/21/2017] [Indexed: 12/25/2022]
Abstract
G4 DNA is a non-canonical DNA structure consisting of a stacked array of Gquartets held together by base pairing between guanine bases. The formation of G4 DNA requires a cluster of guanine-runs within a strand of DNA. Even though the chemistry of this remarkable DNA structure has been under investigation for decades, evidence supporting the biological relevance of G4 DNA has only begun to emerge and point to very important and conserved biological functions. This review will specifically focus on the interplay between transcription and G4 DNA and discuss two alternative but interconnected perspectives. The first part of the review will describe the evidence substantiating the intriguing idea that a shift in DNA structural conformation could be another layer of non-genetic or epigenetic regulator of gene expression and thereby an important determinant of cell fate. The second part will describe the recent genetic studies showing that those genomic loci containing G4 DNA-forming guanine-rich sequences are potential hotspots of genome instability and that the level and orientation of transcription is critical in the materialization of genome instability associated with these sequences.
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Affiliation(s)
- Nayun Kim
- Department of Microbiology and Molecular Genetics, The University of Texas Health Science Center at Houston; The University of Texas Graduate School of Biomedical Sciences, Houston, TX, United States
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44
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Geisler D. Educational Case: Fragile X Syndrome with Size Mosaicism. Acad Pathol 2019; 6:2374289519877550. [PMID: 31633014 PMCID: PMC6769227 DOI: 10.1177/2374289519877550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Revised: 08/18/2019] [Accepted: 08/22/2019] [Indexed: 11/27/2022] Open
Abstract
The following fictional case is intended as a learning tool within the Pathology Competencies for Medical Education (PCME), a set of national standards for teaching pathology. These are divided into three basic competencies: Disease Mechanisms and Processes, Organ System Pathology, and Diagnostic Medicine and Therapeutic Pathology. For additional information, and a full list of learning objectives for all three competencies, seehttp://journals.sagepub.com/doi/10.1177/2374289517715040.
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Affiliation(s)
- Daniel Geisler
- Department of Pathology, University of Pittsburgh Medical Center, PA, USA
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45
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Doll CA, Yergert KM, Appel BH. The RNA binding protein fragile X mental retardation protein promotes myelin sheath growth. Glia 2019; 68:495-508. [PMID: 31626382 DOI: 10.1002/glia.23731] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 09/20/2019] [Accepted: 09/22/2019] [Indexed: 12/13/2022]
Abstract
During development, oligodendrocytes in the central nervous system extend a multitude of processes that wrap axons with myelin. The highly polarized oligodendrocytes generate myelin sheaths on many different axons, which are far removed from the cell body. Neurons use RNA binding proteins to transport, stabilize, and locally translate mRNA in distal domains of neurons. Local synthesis of synaptic proteins during neurodevelopment facilitates the rapid structural and functional changes underlying neural plasticity and avoids extensive protein transport. We hypothesize that RNA binding proteins also regulate local mRNA regulation in oligodendrocytes to promote myelin sheath growth. Fragile X mental retardation protein (FMRP), an RNA binding protein that plays essential roles in the growth and maturation of neurons, is also expressed in oligodendrocytes. To determine whether oligodendrocytes require FMRP for myelin sheath development, we examined fmr1-/- mutant zebrafish and drove FMR1 expression specifically in oligodendrocytes. We found oligodendrocytes in fmr1-/- mutants developed myelin sheaths of diminished length, a phenotype that can be autonomously rescued in oligodendrocytes with FMR1 expression. Myelin basic protein (Mbp), an essential myelin protein, was reduced in myelin tracts of fmr1-/- mutants, but loss of FMRP function did not impact the localization of mbpa transcript in myelin. Finally, expression of FMR1-I304N, a missense allele that abrogates FMRP association with ribosomes, failed to rescue fmr1-/- mutant sheath growth and induced short myelin sheaths in oligodendrocytes of wild-type larvae. Taken together, these data suggest that FMRP promotes sheath growth through local regulation of translation.
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Affiliation(s)
- Caleb A Doll
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, Colorado
| | - Katie M Yergert
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, Colorado
| | - Bruce H Appel
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, Colorado
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Manor E, Gonen R, Sarussi B, Keidar-Friedman D, Kumar J, Tang HT, Tassone F. The role of AGG interruptions in the FMR1 gene stability: A survey in ethnic groups with low and high rate of consanguinity. Mol Genet Genomic Med 2019; 7:e00946. [PMID: 31453660 PMCID: PMC6785435 DOI: 10.1002/mgg3.946] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 07/21/2019] [Accepted: 07/26/2019] [Indexed: 11/07/2022] Open
Abstract
Background The prevalence and the role of AGG interruptions within the FMR1 gene in the normal population is unknown. In this study, we investigated the frequent of AGG loss, in one or two alleles within the normal population. The role of AGG in the FMR1 stability has been assessed by correlating AGG loss to the prevalence of premutation/full mutation in two ethnic groups differing in their consanguinity rate: high versus low consanguinity rate (HCR vs. LCR). Methods The CGG repeat allele size and AGG presence were measured in 6,865 and 6,204 females belonging to the LCR (5%) and HCR (>45%) groups, respectively, by Tripled‐Primed‐PCR technique. Results A lower prevalence of the premutation was observed in the HCR (1:158) as compared to the LCR group (1:128). No full mutation was found in the HCR females while in the LCR group the prevalence found was 1:1,149. Homozygosity rate was higher in the HCR population compared to the LCR group.The overall AGG loss was higher in the HCR population than in the LCR and increased with increased CGG repeat number in both ethnic groups. Conclusions Although we observed a significantly higher rate of homozygosity and AGG loss in the HCR group, this did not affect the prevalence of the premutation and full mutation in this population. Their prevalence was significantly lower than in the LCR population. Finally, we discuss whether the loss of AGG could be also a polymorphic event but not only a stabilizing factor.
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Affiliation(s)
- Esther Manor
- Faculty of Health Science, Ben-Gurion University of the Negev Genetic Institute, Soroka University Medical Center, Beer Sheva, Israel
| | | | | | | | - Jay Kumar
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California Davis, Sacramento, USA
| | - Hiu-Tung Tang
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California Davis, Sacramento, USA
| | - Flora Tassone
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California Davis, Sacramento, USA.,MIND Institute, Medical Center, University of California Davis, Sacramento, USA
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Rajan-Babu IS, Chong SS. Triplet-Repeat Primed PCR and Capillary Electrophoresis for Characterizing the Fragile X Mental Retardation 1 CGG Repeat Hyperexpansions. Methods Mol Biol 2019; 1972:199-210. [PMID: 30847793 DOI: 10.1007/978-1-4939-9213-3_14] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Fragile X mental retardation 1 (FMR1) CGG repeat expansions cause fragile X syndrome-the leading monogenic form of intellectual disability-and increase the risk for fragile X-associated tremor ataxia syndrome and fragile X-associated primary ovarian insufficiency. Southern blot (SB) analysis is the current gold standard test for FMR1 molecular diagnosis. Several polymerase chain reaction (PCR)-based methods are now available for sizing FMR1 CGG repeat expansions. These methods offer higher diagnostic sensitivity and specificity compared to SB analysis, significantly reduce the turnaround time and increase throughput. In this chapter, we describe a triplet-repeat primed PCR protocol that employs capillary electrophoresis to resolve the derived amplicon products, enabling precise determination of the FMR1 genotypes in both males and females and characterization of the CGG repeat structure.
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Affiliation(s)
- Indhu-Shree Rajan-Babu
- Department of Pediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.,Department of Medical Genetics, The University of British Columbia, Vancouver, BC, Canada
| | - Samuel S Chong
- Department of Pediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore. .,Khoo Teck Puat-National University Children's Medical Institute, National University Health System, Singapore, Singapore. .,Department of Laboratory Medicine, National University Hospital, Singapore, Singapore.
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48
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Banez-Coronel M, Ranum LPW. Repeat-associated non-AUG (RAN) translation: insights from pathology. J Transl Med 2019; 99:929-942. [PMID: 30918326 PMCID: PMC7219275 DOI: 10.1038/s41374-019-0241-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 01/29/2019] [Indexed: 12/14/2022] Open
Abstract
More than 40 different neurological diseases are caused by microsatellite repeat expansions. Since the discovery of repeat-associated non-AUG (RAN) translation by Zu et al. in 2011, nine expansion disorders have been identified as RAN-positive diseases. RAN proteins are translated from different types of nucleotide repeat expansions and can be produced from both sense and antisense transcripts. In some diseases, RAN proteins have been shown to accumulate in affected brain regions. Here we review the pathological and molecular aspects associated with RAN protein accumulation for each particular disorder, the correlation between disease pathology and the available in vivo models and the common aspects shared by some of the newly discovered RAN proteins.
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Affiliation(s)
- Monica Banez-Coronel
- Center for NeuroGenetics, University of Florida, Gainesville, FL, 32610, USA
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL, 32610, USA
| | - Laura P W Ranum
- Center for NeuroGenetics, University of Florida, Gainesville, FL, 32610, USA.
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL, 32610, USA.
- Department of Neurology, College of Medicine, University of Florida, Gainesville, FL, 32610, USA.
- McKnight Brain Institute, University of Florida, Gainesville, FL, 32610, USA.
- Genetics Institute, University of Florida, Gainesville, FL, 32610, USA.
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Nolin SL, Glicksman A, Tortora N, Allen E, Macpherson J, Mila M, Vianna-Morgante AM, Sherman SL, Dobkin C, Latham GJ, Hadd AG. Expansions and contractions of the FMR1 CGG repeat in 5,508 transmissions of normal, intermediate, and premutation alleles. Am J Med Genet A 2019; 179:1148-1156. [PMID: 31050164 PMCID: PMC6619443 DOI: 10.1002/ajmg.a.61165] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Revised: 03/21/2019] [Accepted: 04/11/2019] [Indexed: 12/15/2022]
Abstract
Instability of the FMR1 repeat, commonly observed in transmissions of premutation alleles (55–200 repeats), is influenced by the size of the repeat, its internal structure and the sex of the transmitting parent. We assessed these three factors in unstable transmissions of 14/3,335 normal (~5 to 44 repeats), 54/293 intermediate (45–54 repeats), and 1561/1,880 premutation alleles. While most unstable transmissions led to expansions, contractions to smaller repeats were observed in all size classes. For normal alleles, instability was more frequent in paternal transmissions and in alleles with long 3′ uninterrupted repeat lengths. For premutation alleles, contractions also occurred more often in paternal than maternal transmissions and the frequency of paternal contractions increased linearly with repeat size. All paternal premutation allele contractions were transmitted as premutation alleles, but maternal premutation allele contractions were transmitted as premutation, intermediate, or normal alleles. The eight losses of AGG interruptions in the FMR1 repeat occurred exclusively in contractions of maternal premutation alleles. We propose a refined model of FMR1 repeat progression from normal to premutation size and suggest that most normal alleles without AGG interruptions are derived from contractions of maternal premutation alleles.
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Affiliation(s)
- Sarah L Nolin
- Department of Human Genetics, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, New York
| | - Anne Glicksman
- Department of Human Genetics, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, New York
| | - Nicole Tortora
- Department of Human Genetics, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, New York
| | - Emily Allen
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia
| | - James Macpherson
- Wessex Regional Genetics Laboratory, Salisbury NHS District Hospital, Salisbury, United Kingdom
| | - Montserrat Mila
- Biochemical and Molecular Genetics, Hospital Clinic de Barcelona, IDIBAPS and CIBERER, Barcelona, Spain
| | - Angela M Vianna-Morgante
- Department of Genetics and Evolutionary Biology, Institute of Biosciences, Universidade de São Paulo, São Paulo, Brazil
| | - Stephanie L Sherman
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia
| | - Carl Dobkin
- Department of Human Genetics, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, New York
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Salcedo-Arellano MJ, Hagerman RJ, Martínez-Cerdeño V. [Fragile X associated tremor/ataxia syndrome: its clinical presentation, pathology, and treatment]. Rev Neurol 2019; 68:199-206. [PMID: 30805918 PMCID: PMC7001878 DOI: 10.33588/rn.6805.2018457] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The fragile X associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disease associated with the repetition of CGG triplets (55-200 CGG repetitions) in the FMR1 gene. The premutation of the FMR1 gene, contrasting with the full mutation (more than 200 CGG repetitions), presents an increased production of messenger and a similar or slightly decreased production of FMRP protein. FXTAS affects 40% of men and 16% of women carriers of the premutation. It presents with a wide constellation of neurological signs such as intention tremor, cerebellar ataxia, parkinsonism, executive function deficits, peripheral neuropathy and cognitive decline leading to dementia among others. In this review, we present what is currently known about the molecular mechanism, the radiological findings and the pathology, as well as the complexity of the diagnosis and management of FXTAS.
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Affiliation(s)
- María Jimena Salcedo-Arellano
- Department of Pediatrics, University of California Davis
School of Medicine, Sacramento, CA, USA
- Medical Investigation of Neurodevelopmental Disorders
(MIND) Institute, University of California Davis, Sacramento, CA, USA
| | - Randi J Hagerman
- Department of Pediatrics, University of California Davis
School of Medicine, Sacramento, CA, USA
- Medical Investigation of Neurodevelopmental Disorders
(MIND) Institute, University of California Davis, Sacramento, CA, USA
| | - Verónica Martínez-Cerdeño
- Medical Investigation of Neurodevelopmental Disorders
(MIND) Institute, University of California Davis, Sacramento, CA, USA
- Institute for Pediatric Regenerative Medicine and Shriners
Hospitals for Children Northern California, Sacramento, CA, USA
- Department of Pathology and Laboratory Medicine, UC Davis
School of Medicine, Sacramento, CA, USA
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